ATmega325P Atmel Corporation, ATmega325P Datasheet

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... Five Sleep Modes: Idle, ADC Noise Reduction, Power-save, Power-down, and Standby • I/O and Packages – 54/69 Programmable I/O Lines – 64-lead TQFP, 64-pad QFN/MLF, and 100-lead TQFP • Speed Grade: – ATmega325PV/ATmega3250PV MHz @ 1.8 - 5.5V MHz @ 2.7 - 5.5V – ATmega325P/3250P MHz @ 2.7 - 5.5V MHz @ 4.5 - 5.5V • Temperature range: – -40°C to 85°C Industrial • ...

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... Pin Configurations Figure 1-1. ATmega325P/3250P 2 Pinout ATmega3250P DNC 1 2 (RXD/PCINT0) PE0 INDEX CORNER (TXD/PCINT1) PE1 3 4 (XCK/AIN0/PCINT2) PE2 (AIN1/PCINT3) PE3 5 6 (USCK/SCL/PCINT4) PE4 (DI/SDA/PCINT5) PE5 7 8 (DO/PCINT6) PE6 (CLKO/PCINT7) PE7 9 10 VCC GND 11 12 DNC (PCINT24) PJ0 13 14 (PCINT25) PJ1 DNC 15 16 ...

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... Overview The ATmega325P/3250P is a low-power CMOS 8-bit microcontroller based on the AVR enhanced RISC architecture. By executing powerful instructions in a single clock cycle, the ATmega325P/3250P achieves throughputs approaching 1 MIPS per MHz allowing the system designer to optimize power consumption versus processing speed. ...

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... Arithmetic Logic Unit (ALU), allowing two independent registers to be accessed in one single instruction executed in one clock cycle. The resulting architecture is more code efficient while achieving throughputs up to ten times faster than con- ventional CISC microcontrollers. ATmega325P/3250P 4 PF0 - PF7 PA0 - PA7 ...

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... Self-Programmable Flash on a monolithic chip, the Atmel ATmega325P/3250P is a powerful microcontroller that provides a highly flexible and cost effective solution to many embedded con- trol applications. The ATmega325P/3250P AVR is supported with a full suite of program and system develop- ment tools including: C Compilers, Macro Assemblers, Program Debugger/Simulators, In-Circuit Emulators, and Evaluation kits. ...

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... As inputs, Port B pins that are externally pulled low will source current if the pull-up resistors are activated. The Port B pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port B has better driving capabilities than the other ports. Port B also serves the functions of various special features of the ATmega325P/3250P as listed on page 2.3.5 Port C (PC7 ...

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... The Port E pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port E also serves the functions of various special features of the ATmega325P/3250P as listed on page 2.3.8 Port F (PF7..PF0) Port F serves as the analog inputs to the A/D Converter. Port F also serves as an 8-bit bi-directional I/O port, if the A/D Converter is not used. Port pins can provide internal pull-up resistors (selected for each bit) ...

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... AVCC is the supply voltage pin for Port F and the A/D Converter. It should be externally con- nected to V through a low-pass filter. 2.3.16 AREF This is the analog reference pin for the A/D Converter. ATmega325P/3250P 8 308. Shorter pulses are not guaranteed to generate a reset. , even if the ADC is not used. If the ADC is used, it should be connected ”System and Reset CC 8023F– ...

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... Resources A comprehensive set of development tools, application notes and datasheets are available for download on http://www.atmel.com/avr. 8023F–AVR–07/09 ATmega325P/3250P 9 ...

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... For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”, and “SBI” instructions must be replaced with instructions that allow access to extended I/O. Typically “LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and “CBR”. ATmega325P/3250P 10 1. ...

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... This allows single-cycle Arithmetic Logic Unit (ALU) operation typ- 8023F–AVR–07/09 Block Diagram of the AVR Architecture Program Flash Counter Program Memory Instruction Register Instruction Decoder Control Lines ATmega325P/3250P Data Bus 8-bit Status and Control Interrupt Unit General Purpose SPI Registrers Unit Watchdog ...

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... SPI, and other I/O functions. The I/O Memory can be accessed directly the Data Space locations following those of the Register File, 0x20 - 0x5F. In addition, the ATmega325P/3250P has Extended I/O space from 0x60 - 0xFF in SRAM where only the ST/STS/STD and LD/LDS/LDD instructions can be used. ...

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... Bit 2 – N: Negative Flag The Negative Flag N indicates a negative result in an arithmetic or logic operation. See the “Instruction Set Description” for detailed information. 8023F–AVR–07/ R/W R/W R/W R ⊕ V ATmega325P/3250P R/W R/W R/W R SREG 13 ...

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... Data Space. Although not being physically imple- mented as SRAM locations, this memory organization provides great flexibility in access of the registers, as the X-, Y- and Z-pointer registers can be set to index any register in the file. ATmega325P/3250P 14 shows the structure of the 32 general purpose working registers in the CPU. ...

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... Data is pushed onto the stack Return address is pushed onto the stack with a subroutine call or Decremented by 2 interrupt Incremented by 1 Data is popped from the stack Incremented by 2 Return address is popped from the stack with return from subroutine or return from interrupt ATmega325P/3250P Figure . R26 (0x1A ...

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... Instruction Fetch 2nd Instruction Execute 3rd Instruction Execute Figure 2 operation using two register operands is executed, and the result is stored back to the destina- tion register. Figure 2. Single Cycle ALU Operation Register Operands Fetch ALU Operation Execute ATmega325P/3250P SP15 SP14 SP13 SP7 ...

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... No interrupt will be executed after the CLI instruction, even if it occurs simultaneously with the 8023F–AVR–07/09 for details. ”Interrupts” on page 53 ”Boot Loader Support – Read-While-Write Self-Programming” on page ATmega325P/3250P ”Memory Program- ”Interrupts” on page 53. The list also for more information. ...

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... A return from an interrupt handling routine takes four clock cycles. During these four clock cycles, the Program Counter (two bytes) is popped back from the Stack, the Stack Pointer is incremented by two, and the I-bit in SREG is set. ATmega325P/3250P 18 ; store SREG value ; disable interrupts during timed sequence ...

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... Boot Program section and Application Program section. The Flash memory has an endurance of at least 10,000 write/erase cycles. The ATmega325P/3250P Program Counter (PC bits wide, thus addressing the 16K program memory locations. The operation of Boot Program section and associated Boot Lock bits for software protection are described in detail in gramming” ...

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... When using register indirect addressing modes with automatic pre-decrement and post-incre- ment, the address registers X, Y, and Z are decremented or incremented. The 32 general purpose working registers, 64 I/O Registers, 160 Extended I/O Registers, and the 2,048 bytes of internal data SRAM in the ATmega325P/3250P are all accessible through all ATmega325P/3250P 20 ...

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... Figure 7-3. 7.4 EEPROM Data Memory The ATmega325P/3250P contains 1K bytes of data EEPROM memory organized as a sep- arate data space, in which single bytes can be read and written. The EEPROM has an endurance of at least 100,000 write/erase cycles. The access between the EEPROM and the CPU is described in the following, specifying the EEPROM Address Registers, the EEPROM Data Register, and the EEPROM Control Register ...

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... When using the I/O specific commands IN and OUT, the I/O addresses 0x00 - 0x3F must be used. When addressing I/O Registers as data space using LD and ST instructions, 0x20 must be added to these addresses. The ATmega325P/3250P is a complex microcontroller with more peripheral units than can be supported within the 64 location ...

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... EEAR7 EEAR6 EEAR5 R/W R/W R EEAR10 is only valid for ATmega645P and ATmega6450P MSB R/W R/W R ATmega325P/3250P – – EEAR10 EEAR9 EEAR4 EEAR3 EEAR2 EEAR1 R/W R/W R/W R/W R/W R ...

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... EEPROM Master Write Enable will time-out interrupt routine accessing the EEPROM is interrupting another EEPROM access, the EEAR or EEDR Register will be modified, causing the interrupted EEPROM access to fail recommended to have the Global Interrupt Flag cleared during all the steps to avoid these problems. ATmega325P/3250P ...

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... Flash Boot Loader is present in the software. If such code is present, the EEPROM write function must also wait for any ongoing SPM command to finish. 8023F–AVR–07/09 EEPROM Programming Time Number of Calibrated RC Oscillator Cycles 27,072 ATmega325P/3250P Table 7-1 lists the typical pro- Typical Programming Time 3 ...

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... EECR |= (1<<EEMWE); /* Start eeprom write by setting EEWE */ EECR |= (1<<EEWE); } The next code examples show assembly and C functions for reading the EEPROM. The exam- ples assume that interrupts are controlled so that no interrupts will occur during execution of these functions. ATmega325P/3250P 26 ; 8023F–AVR–07/09 ...

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... General Purpose I/O Registers The ATmega325P/3250P contains three General Purpose I/O Registers. These registers can be used for storing any information, and they are particularly useful for storing global variables and Status Flags. General Purpose I/O Registers within the address range 0x00 - 0x1F are directly bit-accessible using the SBI, CBI, SBIS, and SBIC instructions ...

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... GPIOR0 – General Purpose I/O Register 0 Bit 0x1E (0x3E) Read/Write Initial Value ATmega325P/3250P MSB R/W R/W R/W R LSB R/W R/W R/W R 8023F–AVR–07/09 GPIOR0 ...

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... AVR Clock I/O Control Unit clk ASY Clock Multiplexer Timer/Counter External Clock Oscillator is halted, enabling USI start condition detection in all sleep modes. I/O ATmega325P/3250P CPU Core RAM clk CPU clk FLASH Reset Logic Watchdog Timer Source clock Watchdog clock Watchdog Oscillator Crystal ...

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... Internal RC Oscillator with longest start-up time and an initial system clock prescaling of 8, resulting in 1.0 MHz system clock. This default setting ensures that all users can make their desired clock source setting using an In-System or Parallel programmer. ATmega325P/3250P 30 ASY Device Clocking Options Select 1. For all fuses “ ...

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... Start-up Times for the Crystal Oscillator Clock Selection Start-up Time from Power-down and SUT1..0 Power-save (1) 00 258 CK (1) 01 258 CK ( ATmega325P/3250P Figure 8-2. Either a quartz crystal or a XTAL2 XTAL1 GND Table 8-3. Recommended Range for Capacitors C1 and C2 for Use with Crystals (pF) – ...

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... The Low-frequency Crystal Oscillator is optimized for use with a 32.768 kHz watch crystal. When selecting crystals, load capasitance and crystal’s Equivalent Series Resistance, ESR must be taken into consideration. Both values are specified by the crystal vendor. ATmega325P/3250P oscillator is optimized for very low power consumption, and thus when selecting crystals, see 9.0 pF and 12.5 pF crystals Table 8-5 ...

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... The device is shipped with this option selected. 2. The frequency ranges are preliminary values. Actual values are TBD MHz frequency exceeds the specification of the device (depends on V Fuse can be programmed in order to divide the internal frequency by 8. ATmega325P/3250P = 5.0V) Recommended Usage CC Fast rising power or BOD enabled ...

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... When applying an external clock required to avoid sudden changes in the applied clock fre- quency to ensure stable operation of the MCU. A variation in frequency of more than 2% from ATmega325P/3250P 34 34. Start-up times for the internal calibrated RC Oscillator clock selection Start-up Time from Power- down and Power-save ...

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... System Clock Prescaler The ATmega325P/3250P system clock can be divided by setting the Clock Prescale Register – CLKPR. This feature can be used to decrease power consumption when the requirement for processing power is low. This can be used with all clock source options, and it will affect the clock frequency of the CPU and all synchronous peripherals ...

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... These bits can be written run-time to vary the clock frequency to suit the application requirements. As the divider divides the master clock input to the MCU, the speed of all synchro- nous peripherals is reduced when a division factor is used. The division factors are given in Table 8-10. ATmega325P/3250P ...

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... ATmega325P/3250P CLKPS0 Clock Division Factor 128 0 256 1 Reserved 0 Reserved 1 Reserved 0 Reserved 1 Reserved 0 Reserved 1 Reserved 37 ...

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... SRAM are unaltered when the device wakes up from sleep reset occurs during sleep mode, the MCU wakes up and executes from the Reset Vector. 8023F–AVR–07/09 for more details. presents the different clock systems in the ATmega325P/3250P, and Active Clock Domains and Wake-up Sources in the Different Sleep Modes. Active Clock Domains X ...

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... ADC Conversion Complete interrupt, only an External Reset, a Watchdog Reset, a Brown-out Reset, USI start condition interrupt, a Timer/Counter2 interrupt, an SPM/EEPROM ready inter- rupt, an external level interrupt on INT0 or a pin change interrupt can wake up the MCU from ADC Noise Reduction mode. ATmega325P/3250P 39 level has dropped during the sleep period ...

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... Module shutdown can be used in IDLE mode and active mode to reduce the overall power con- sumption. In all other sleep modes, the clock is already stopped. 8023F–AVR–07/09 ATmega325P/3250P ”External Interrupts” on page 58 ”Clock Sources” on page 30. ...

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... When entering a sleep mode, all port pins should be configured to use minimum power. The most important is then to ensure that no pins drive resistive loads. In sleep modes where both the I/O clock (clk be disabled. This ensures that no power is consumed by the input logic when not needed. In ATmega325P/3250P 41 ”Analog Comparator” on page 203 for details on the start-up time. ...

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... Input Enable and Sleep Modes” on page 67 /2, the input buffer will use excessive power input pin can cause significant current even in active mode. Digital CC ”DIDR1 – Digital Input Disable Register 1” on page 205 for details. ATmega325P/3250P for details on and ”DIDR0 – Digital 42 ...

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... The BODS bit must be written to logic one in order to turn off BOD during sleep, see on page BODSE in MCUCR. To disable BOD in relevant sleep modes, both BODS and BODSE must first be set to one. Then, to set the BODS bit, BODS must be set to one and BODSE must be set to zero within four clock cycles. ATmega325P/3250P – ...

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... The analog comparator cannot use the ADC input MUX when the ADC is shut down. Note: 8023F–AVR–07/ – – – R The Analog Comparator is disabled using the ACD-bit in the and Status Register” on page 204. ATmega325P/3250P – PRTIM1 PRSPI PRUSART0 R/W R/W R ”ACSR – Analog Comparator Control 0 PRADC ...

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... Reset Sources The ATmega325P/3250P has five sources of reset: • Power-on Reset. The MCU is reset when the supply voltage is below the Power-on Reset threshold (V • External Reset. The MCU is reset when a low level is present on the RESET pin for longer than the minimum pulse length. • ...

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... A Power-on Reset (POR) circuit ensures that the device is reset from Power-on. Reaching the Power-on Reset threshold voltage invokes the delay counter, which determines how long the device is kept in RESET after V when V CC Figure 10-2. MCU Start-up, RESET Tied to V TIME-OUT INTERNAL ATmega325P/3250P 46 Power-on Reset Circuit Brown-out Reset Circuit Pull-up Resistor SPIKE ...

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... Figure 10-4. External Reset During Operation 10.2.3 Brown-out Detection ATmega325P/3250P has an On-chip Brown-out Detection (BOD) circuit for monitoring the V level during operation by comparing fixed trigger level. The trigger level for the BOD can be selected by the BODLEVEL Fuses. The trigger level has a hysteresis to ensure spike free Brown-out Detection ...

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... Figure 10-6. Watchdog Reset During Operation 10.3 Internal Voltage Reference ATmega325P/3250P features an internal bandgap reference. This reference is used for Brown- out Detection, and it can be used as an input to the Analog Comparator or the ADC. 10.3.1 Voltage Reference Enable Signals and Start-up Time The voltage reference has a start-up time that may influence the way it should be used. The start-up time is given in reference is not always turned on ...

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... Timer. The Watchdog Timer is also reset when it is disabled and when a Chip Reset occurs. Eight different clock cycle periods can be selected to determine the reset period. If the reset period expires without another Watchdog Reset, the ATmega325P/3250P resets and executes from the Reset Vector. For timing details on the Watchdog Reset, refer to 51 ...

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... This bit is set if a Power-on Reset occurs. The bit is reset only by writing a logic zero to the flag. To make use of the Reset Flags to identify a reset condition, the user should read and then Reset the MCUSR as early as possible in the program. If the register is cleared before another reset occurs, the source of the reset can be found by examining the Reset Flags. ATmega325P/3250P ...

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... Oscillator Cycles 0 0 16K cycles 0 1 32K cycles 1 0 64K cycles 1 1 128K cycles 0 0 256K cycles 0 1 512K cycles 1 0 1,024K cycles 1 1 2,048K cycles ATmega325P/3250P WDE WDP2 WDP1 WDP0 R/W R/W R/W R Typical Time-out at Typical Time-out 3. 5. ...

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... WDTCR, r16 ret C Code Example void WDT_off(void Reset WDT */ __watchdog_reset(); /* Write logical one to WDCE and WDE */ WDTCR |= (1<<WDCE) | (1<<WDE); /* Turn off WDT */ WDTCR = 0x00; } Note: ATmega325P/3250P 52 (1) r16, WDTCR (1) 1. See Section “5.” on page 10. 8023F–AVR–07/09 ...

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... ATmega325P/3250P. For a general explanation of the AVR interrupt handling, refer to and Interrupt Handling” ...

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... Reset Vector is in the Application section while the Interrupt Vectors are in the Boot section or vice versa. Table 11-2. BOOTRST Note: The most typical and general program setup for the Reset and Interrupt Vector Addresses in ATmega325P/3250P is: Address 0x0000 0x0002 0x0004 0x0006 0x0008 0x000A 0x000C 0x000E ...

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... SPH,r16 ; Set Stack Pointer to top of RAM ldi r16,low(RAMEND) out SPL,r16 sei <instr> xxx ATmega325P/3250P ; Main program start ; Set Stack Pointer to top of RAM ; Enable interrupts Comments ; Set Stack Pointer to top of RAM ; Enable interrupts ; IRQ0 Handler ; PCINT0 Handler ; ; Store Program Memory Ready Handler ...

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... Interrupts will automatically be disabled while this sequence is executed. Interrupts are disabled in the cycle IVCE is set, and they remain disabled until after the instruction following the write to IVSEL. If IVSEL is not written, interrupts remain disabled for four cycles. The I-bit in the Status Register is unaffected by the automatic disabling. Note: ATmega325P/3250P 56 jmp RESET jmp ...

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... Move_interrupts(void 8023F–AVR–07/09 ; Enable change of Interrupt Vectors ori r16, (1<<IVCE) out MCUCR, r16 ; Move interrupts to Boot Flash section ori r17, (1<<IVSEL) out MCUCR, r17 ret /* Enable change of Interrupt Vectors */ MCUCR |= (1<<IVCE); /* Move interrupts to Boot Flash section */ MCUCR |= (1<<IVSEL); ATmega325P/3250P 57 ...

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... Clock and Clock Options” on page Notes: 8023F–AVR–07/09 ”EICRA – External Interrupt Control Register A” on page 1. PCMSK3 and PCMSK2 are only present in ATmega3250P. 2. PCINT30:16 are only present in ATmega3250P. Only PCINT15:0 are present in ATmega325P. See ”Pin Configurations” on page 2 ATmega325P/3250P (1) ...

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... If edge or toggle interrupt is selected, pulses that last longer than one clock period will generate an interrupt. Shorter pulses are not guaranteed to generate an interrupt. If low level interrupt is selected, the low level must be held until the completion of the currently executing instruction to generate an interrupt. ATmega325P/3250P 59 pin_lat PCINT(0) ...

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... The corresponding interrupt of Pin Change Interrupt Request is executed from the PCINT3 Interrupt Vector. PCINT30:24 pins are enabled individually by the PCMSK3 Register. This bit is reserved bit in ATmega325P and should always be written to zero. • Bit 6 – PCIE2: Pin Change Interrupt Enable 2 When the PCIE2 bit is set (one) and the I-bit in the Status Register (SREG) is set (one), pin change interrupt 2 is enabled ...

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... Interrupt Vector. The flag is cleared when the interrupt routine is executed. Alter- natively, the flag can be cleared by writing a logical one to it. This bit is reserved bit in ATmega325P and will always be read as zero. • Bit 6 – PCIF2: Pin Change Interrupt Flag 2 When a logic change on any PCINT24:16 pin triggers an interrupt request, PCIF2 becomes set (one) ...

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... R/W R PCMSK3 and PCMSK2 are only present in ATmega3250P PCINT15 PCINT14 PCINT13 PCINT12 R/W R/W R PCINT7 PCINT6 PCINT5 PCINT4 R/W R/W R/W R ATmega325P/3250P PCINT27 PCINT26 PCINT25 R/W R/W R/W R PCINT19 PCINT18 PCINT17 R/W R/W R/W R PCINT11 ...

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... Most port pins are multiplexed with alternate functions for the peripheral features on the device. How each alternate function interferes with the port pin is described in 8023F–AVR–07/09 Figure 13-1. Refer to Pxn C pin ”Register Description” on page ATmega325P/3250P ”Electrical Characteristics” on page 304 R pu Logic See Figure "General Digital I/O" for Details 85. ...

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... If PORTxn is written logic one when the pin is configured as an input pin, the pull-up resistor is activated. To switch the pull-up resistor off, PORTxn has to be written logic zero or the pin has to ATmega325P/3250P 64 69. Refer to the individual module sections for a full description of the alter- ...

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... Input 1 1 Input 0 X Output 1 X Output Figure 13-2, the PINxn Register bit and the preceding latch con- pd,max ATmega325P/3250P Pull-up Comment No Tri-state (Hi-Z) Yes Pxn will source current if ext. pulled low. No Tri-state (Hi-Z) No Output Low (Sink) No Output High (Source) Figure 13-3 shows a timing dia- and t respectively ...

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... The resulting pin values are read back again, but as previously discussed, a nop instruction is included to be able to read back the value recently assigned to some of the pins. ATmega325P/3250P 66 SYSTEM CLK ...

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... Figure 13-2, the digital input signal can be clamped to ground at the input of the ”Alternate Port Functions” on page ATmega325P/3250P /2. CC 69. 67 ...

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... In this case, the pull-up will be disabled during reset. If low power consumption during reset is important recommended to use an external pull-up or pull-down. Connecting unused pins directly to V accidentally configured as an output. ATmega325P/3250P 68 or GND is not recommended, since this may cause excessive currents if the pin is CC ...

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... SLEEP, and PUD are common to all ports. All other signals are unique for each pin. summarizes the function of the overriding signals. The pin and port indexes from are not shown in the succeeding tables. The overriding signals are generated internally ATmega325P/3250P Figure 13-2 can be overridden by ...

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... AIO The following subsections shortly describe the alternate functions for each port, and relate the overriding signals to the alternate function. Refer to the alternate function description for further details. Some pins are connected to different LCS segments on ATmega325P and ATmega3250P. See pinout on ATmega325P/3250P 70 ...

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... OC0A/PCINT12 (Output Compare and PWM Output A for Timer/Counter0 or Pin Change Interrupt12). MISO/PCINT11 (SPI Bus Master Input/Slave Output or Pin Change Interrupt11). MOSI/PCINT10 (SPI Bus Master Output/Slave Input or Pin Change Interrupt10). SCK/PCINT9 (SPI Bus Serial Clock or Pin Change Interrupt9). SS/PCINT8 (SPI Slave Select input or Pin Change Interrupt8). ATmega325P/3250P Table 13-3. 71 ...

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... When the SPI is enabled as a Master, the data direction of this pin is controlled by DDB0. When the pin is forced input, the pull-up can still be controlled by the PORTB0 bit PCINT8, Pin Change Interrupt Source 8: The PB0 pin can serve as an external interrupt source. ATmega325P/3250P 72 8023F–AVR–07/09 ...

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... SPI SLAVE SPI MSTR OUTPUT OUTPUT – – PCINT11 • PCIE1 PCINT10 • PCIE1 1 1 PCINT11 INPUT PCINT10 INPUT SPI MSTR INPUT SPI SLAVE INPUT – – ATmega325P/3250P PB5/OC1A/ PB4/OC0A/ PCINT13 PCINT12 OC1A ENABLE OC0A ENABLE OC1A OC0A – ...

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... DDOV PVOE PVOV PTOE DIEOE DIEOV DI AIO ATmega325P/3250P 74 Port D Pins Alternate Functions (SEG refers to 100-pin/64-pin pinout) Alternate Function INT0 (External Interrupt0 Input) ICP1 (Timer/Counter1 Input Capture pin) relates the alternate functions of Port D to the overriding signals shown in 69. Overriding Signals for Alternate Functions in PD3:PD0 ...

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... USCK/SCL/PCINT4 (USART0 External Clock Input/Output or TWI Serial Clock or Pin Change Interrupt4) AIN1/PCINT3 (Analog Comparator Negative Input or Pin Change Interrupt3) XCK/AIN0/ PCINT2 (USART0 External Clock or Analog Comparator Positive Input or Pin Change Interrupt2) TXD/PCINT1 (USART0 Transmit Pin or Pin Change Interrupt1) RXD/PCINT0 (USART0 Receive Pin or Pin Change Interrupt0) ATmega325P/3250P Table 13-8. 75 ...

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... Table 13-9 shown in Table 13-9. Signal Name PUOE PUOV DDOE DDOV PVOE PVOV PTOE DIEOE DIEOV DI AIO Note: ATmega325P/3250P 76 and Table 13-10 relates the alternate functions of Port E to the overriding signals Figure 13-5 on page 69. Overriding Signals for Alternate Functions PE7:PE4 PE6/DO/ PE7/PCINT7 PCINT6 (1) ...

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... ADC6/TDO (ADC input channel 6 or JTAG Test Data Output) ADC5/TMS (ADC input channel 5 or JTAG Test mode Select) ADC4/TCK (ADC input channel 4 or JTAG Test ClocK) ADC3 (ADC input channel 3) ADC2 (ADC input channel 2) ADC1 (ADC input channel 1) ADC0 (ADC input channel 0) ATmega325P/3250P PE1/TXD/ PCINT1 TXEN 0 TXEN 1 ...

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... I/O pin. • ADC3 - ADC0 – Port F, Bit 3:0 Analog to Digital Converter, Channel 3-0. Table 13-12. Overriding Signals for Alternate Functions in PF7:PF4 Signal Name PUOE PUOV DDOE DDOV PVOE PVOV PTOE DIEOE DIEOV DI AIO ATmega325P/3250P PF7/ADC7/TDI PF6/ADC6/TDO JTAGEN JTAGEN 1 1 JTAGEN JTAGEN SHIFT_IR + 0 SHIFT_DR ...

Page 79

... T0(Timer/Counter0 Clock Input) T1(Timer/Counter1 Clock Input) – – – 1. Port G, PG5 is input only. Pull-up is always on. See Table 25-3 on page 272 for RSTDISBL fuse. and Table 13-15 relates the alternate functions of Port G to the overriding signals Figure 13-5 on page 69. ATmega325P/3250P PF1/ADC1 PF0/ADC0 – ...

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... PCINT22 – Port H, Bit 6 PCINT22, Pin Change Interrupt Source 22: The PH6 pin can serve as an external interrupt source. • PCINT21 – Port H, Bit 5 PCINT21, Pin Change Interrupt Source 21: The PH5 pin can serve as an external interrupt source. ATmega325P/3250P 80 PG4/ ...

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... PCINT23 • PCIE0 PCINT22 • PCIE0 0 0 PCINT23 INPUT PCINT22 INPUT – – ATmega325P/3250P PH5/PCINT21 PH4/PCINT20 – – PCINT21 • PCIE0 PCINT20 • PCIE0 0 0 PCINT21 INPUT PCINT20 INPUT – ...

Page 82

... PCINT29 – Port J, Bit 5 PCINT29, Pin Change Interrupt Source 29: The PE29 pin can serve as an external interrupt source. • PCINT28 – Port J, Bit 4 PCINT28, Pin Change Interrupt Source 28: The PE28 pin can serve as an external interrupt source. ATmega325P/3250P 82 PH3/PCINT19 PH2/PCINT18 0 0 ...

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... Figure 13-5 on page 69. PJ7 PJ6/PCINT30 – – 0 PCINT30 • PCIE0 0 0 – – – – ATmega325P/3250P PJ5/PCINT29 PJ4/PCINT28 – – PCINT29 • PCIE0 PCINT28 • PCIE0 0 0 – – – – 83 ...

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... Table 13-21. Overriding Signals for Alternate Functions in PH3:0 Signal Name PUOE PUOV DDOE DDOV PVOE PVOV PTOE DIEOE DIEOV DI AIO ATmega325P/3250P 84 PJ3/PCINT27 PJ2/PCINT26 – – PCINT27 • PCIE0 PCINT26 • PCIE0 0 0 – – – – ...

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... PORTB4 R/W R/W R/W R DDB7 DDB6 DDB5 DDB4 R/W R/W R/W R PINB7 PINB6 PINB5 PINB4 R/W R/W R/W R/W N/A N/A N/A N/A ATmega325P/3250P – – IVSEL IVCE R R R/W R PORTA3 PORTA2 PORTA1 PORTA0 R/W R/W R/W R DDA3 DDA2 DDA1 DDA0 ...

Page 86

... PIND – Port D Input Pins Address Bit 0x09 (0x29) Read/Write Initial Value 13.4.14 PORTE – Port E Data Register Bit 0x0E (0x2E) Read/Write Initial Value 13.4.15 DDRE – Port E Data Direction Register Bit 0x0D (0x2D) Read/Write Initial Value ATmega325P/3250P PORTC7 PORTC6 PORTC5 PORTC4 R/W R/W R/W R ...

Page 87

... – – PING5 PING4 R N/A ( PORTH7 PORTH6 PORTH5 PORTH4 R/W R/W R/W R ATmega325P/3250P PINE3 PINE2 PINE1 PINE0 R/W R/W R/W R/W N/A N/A N/A N PORTF3 PORTF2 PORTF1 PORTF0 R/W R/W R/W R DDF3 DDF2 DDF1 DDF0 ...

Page 88

... PORTJ – Port J Data Register Bit (0xDD) Read/Write Initial Value 13.4.27 DDRJ – Port J Data Direction Register Bit (0xDC) Read/Write Initial Value 13.4.28 PINJ – Port J Input Pins Address Bit (0xDB) Read/Write Initial Value Note: ATmega325P/3250P 88 ( DDH7 DDH6 DDH5 R/W R ...

Page 89

... Control Logic direction BOTTOM TOP Timer/Counter TCNTn = 0 = 0xFF = OCRn ATmega325P/3250P Figure 14-1. For the actual placement and ”Pinout ATmega325P” on page ”Register Description” on page 102. TOVn (Int.Req.) Clock Select clk Tn Edge Tn Detector ( From Prescaler ) OCn (Int.Req.) Waveform OCn Generation T0 3 ...

Page 90

... Figure 14-2. Counter Unit Block Diagram Signal description (internal signals): count direction clear ATmega325P/3250P 90 for details. The compare match event will also set the Compare Flag (OCF0A) Table 14-1 are also used extensively throughout the document. Definitions of Timer/Counter values. ...

Page 91

... Timer/Counter clock, referred to as clk Tn Signalize that TCNT0 has reached maximum value. Signalize that TCNT0 has reached minimum value (zero). ). clk can be generated from an external or internal clock source present or not. A CPU write overrides (has priority over) all counter clear or T0 94. ATmega325P/3250P in the following ...

Page 92

... The OCR0A Register access may seem complex, but this is not case. When the double buffer- ing is enabled, the CPU has access to the OCR0A Buffer Register, and if double buffering is disabled the CPU will access the OCR0A directly. ATmega325P/3250P 92 (See Section “14.7” on page shows a block diagram of the Output Compare unit ...

Page 93

... PORT) that are affected by the COM0A1:0 bits are shown. When referring to the OC0A state, the reference is for the internal OC0A Register, not the OC0A pin System Reset occur, the OC0A Register is reset to “0”. 8023F–AVR–07/09 ATmega325P/3250P Figure 14-4 shows a sim- 93 ...

Page 94

... Waveform Generation mode bits do. The COM0A1:0 bits control whether the PWM output generated should be inverted or not (inverted or non-inverted PWM). For non-PWM modes the COM0A1:0 bits control whether the output should be set, cleared, or toggled at a compare match For detailed timing information refer to ter Timing Diagrams” on page ATmega325P/3250P 94 COMnx1 Waveform COMnx0 D ...

Page 95

... Compare Output mode bits to toggle mode (COM0A1:0 = 1). The OC0A value will not be visible on the port pin unless the data direction for 8023F–AVR–07/09 Figure ATmega325P/3250P 14-5. The counter value (TCNT0) OCnx Interrupt Flag Set (COMnx1 ...

Page 96

... Figure 14-6. Fast PWM Mode, Timing Diagram TCNTn OCn OCn Period The Timer/Counter Overflow Flag (TOV0) is set each time the counter reaches MAX. If the inter- rupt is enabled, the interrupt handler routine can be used for updating the compare value. ATmega325P/3250P 96 f clk_I ------------------------------------------------- - OCnx ⋅ ...

Page 97

... The TCNT0 value is in the timing diagram shown as a histogram for illustrating the dual-slope operation. The diagram includes non-inverted and inverted PWM outputs. The small horizontal line marks on the TCNT0 slopes represent compare matches between OCR0A and TCNT0. 8023F–AVR–07/09 ATmega325P/3250P Table 14-4 on page f clk_I/O ...

Page 98

... Compare Match. The point of this transition is to guarantee symmetry around BOT- TOM. There are two cases that give a transition without Compare Match. • OCR0A changes its value from MAX, like in OCn pin value is the same as the result of a down-counting Compare Match. To ensure ATmega325P/3250P ...

Page 99

... I/O MAX - 1 shows the same timing data, but with the prescaler enabled. I/O Tn /8) I/O MAX - 1 shows the setting of OCF0A in all modes except CTC mode. I/O Tn /8) I/O OCRnx - 1 ATmega325P/3250P ) is therefore shown MAX BOTTOM /8) clk_I/O MAX BOTTOM OCRnx OCRnx + 1 OCRnx Value BOTTOM + 1 BOTTOM + 1 /8) clk_I/O ...

Page 100

... T1/T0 synchronization and edge detector logic. The registers are clocked at the positive edge of the internal system clock ( is transparent in the high period of the internal system clock. ATmega325P/3250P 100 shows the setting of OCF0A and the clearing of TCNT0 in CTC mode. ...

Page 101

... LE clk I/O Synchronization < f /2) given a 50/50% duty cycle. Since the edge detector uses ExtClk clk_I/O I/O Clear Synchronization Synchronization clk 1. The synchronization logic on the input pins ( ATmega325P/3250P pulse for each positive (CSn2 negative Edge Detector (1) T1 T1/T0) is shown in Figure Tn_sync (To Clock Select Logic) /2 ...

Page 102

... These bits control the Output Compare pin (OC0A) behavior. If one or both of the COM0A1:0 bits are set, the OC0A output overrides the normal port functionality of the I/O pin it is connected to. However, note that the Data Direction Register (DDR) bit corresponding to the OC0A pin must be set in order to enable the output driver. ATmega325P/3250P 102 7 6 ...

Page 103

... A special case occurs when OCR0A equals TOP and COM0A1 is set. In this case, the com- pare match is ignored, but the set or clear is done at TOP. See page 97 for more details. ATmega325P/3250P (1) ”Fast PWM Mode” on (1) ”Phase Correct PWM Mode” on ...

Page 104

... A match can be used to generate an Output Compare interrupt generate a waveform output on the OC0A pin. 14.10.4 TIMSK0 – Timer/Counter 0 Interrupt Mask Register Bit (0x6E) Read/Write Initial Value ATmega325P/3250P 104 Clock Select Bit Description CS01 CS00 Description clock source (Timer/Counter stopped) ...

Page 105

... TSM – – – R ATmega325P/3250P 105. ”TIFR0 – Timer/Counter – – OCF0A TOV0 R R R/W R – – PSR2 PSR10 R R R/W R ...

Page 106

... When this bit is one, Timer/Counter1 and Timer/Counter0 prescaler will be Reset. This bit is nor- mally cleared immediately by hardware, except if the TSM bit is set. Note that Timer/Counter1 and Timer/Counter0 share the same prescaler and a reset of this prescaler will affect both timers. ATmega325P/3250P 106 8023F–AVR–07/09 ...

Page 107

... The PRTIM1 bit in enable the Timer/Counter1 module. 8023F–AVR–07/09 ”Pinout ATmega3250P” on page ”Register Description” on page 128. ”PRR – Power Reduction Register” on page 44 ATmega325P/3250P Figure 15-1. For the actual 2. CPU accessible I/O Registers, must be written to zero to 107 ...

Page 108

... The output from the Clock Select logic is referred to as the timer clock (clk The double buffered Output Compare Registers (OCR1A/B) are compared with the Timer/Coun- ter value at all time. The result of the compare can be used by the Waveform Generator to generate a PWM or variable frequency output on the Output Compare pin (OC1A/B). ATmega325P/3250P 108 Count Clear ...

Page 109

... The counter reaches the TOP when it becomes equal to the highest value in the count sequence. The TOP value can be assigned to be one of the fixed values: 0x00FF, 0x01FF, or 0x03FF the value stored in the OCR1A or ICR1 Register. The assignment is dependent of the mode of operation. ATmega325P/3250P (”Analog 109 ...

Page 110

... Timer Regis- ters, then the result of the access outside the interrupt will be corrupted. Therefore, when both ATmega325P/3250P 110 (1) (1) 1 ...

Page 111

... Restore global interrupt flag out SREG,r18 ret (1) unsigned char sreg; unsigned int i; /* Save global interrupt flag */ sreg = SREG; /* Disable interrupts */ __disable_interrupt(); /* Read TCNT1 into TCNT1; /* Restore global interrupt flag */ SREG = sreg; return i; 1. See Section “5.” on page 10. ATmega325P/3250P 111 ...

Page 112

... Timer/Counter Clock Sources The Timer/Counter can be clocked by an internal or an external clock source. The clock source is selected by the Clock Select logic which is controlled by the Clock Select (CS12:0) bits located in the sources and prescaler, see ATmega325P/3250P 112 (1) (1) 1. See Section “5.” on page 10. ...

Page 113

... Signalize that TCNT1 has reached minimum value (zero). ). The clk can be generated from an external or internal clock source present or not. A CPU write overrides (has priority over) all counter clear ”Modes of Operation” on page ATmega325P/3250P TOVn (Int.Req.) Clock Select Edge Detector clk Tn Control Logic ( From Prescaler ) TOP BOTTOM 119 ...

Page 114

... When the CPU reads the ICR1H I/O location it will access the TEMP Register. The ICR1 Register can only be written when using a Waveform Generation mode that utilizes the ICR1 Register for defining the counter’s TOP value. In these cases the Waveform Genera- ATmega325P/3250P 114 DATA BUS TEMP (8-bit) ...

Page 115

... Changing the edge sensing must be done as early as possible after the ICR1 Register has been read. After a change of the edge, the Input Capture Flag (ICF1) must be 8023F–AVR–07/09 110. ATmega325P/3250P ”Accessing 16-bit Registers” (Figure 14-8 on page 101). The edge detector is also ...

Page 116

... For the Normal and Clear Timer on Compare (CTC) modes of operation, the double buffering is disabled. The double buffering synchronizes the update of the OCR1x Com- pare Register to either TOP or BOTTOM of the counting sequence. The synchronization ATmega325P/3250P 116 (See Section “15.9” on page shows a block diagram of the Output Compare unit. The small “ ...

Page 117

... Compare Match Output Unit The Compare Output mode (COM1x1:0) bits have two functions. The Waveform Generator uses the COM1x1:0 bits for defining the Output Compare (OC1x) state at the next compare match. 8023F–AVR–07/09 110. ATmega325P/3250P ”Accessing 16-bit Registers” 117 ...

Page 118

... For all modes, setting the COM1x1 tells the Waveform Generator that no action on the OC1x Register performed on the next compare match. For compare output actions in the non-PWM modes refer to page 129, and for phase correct and phase and frequency correct PWM refer to page 129. ATmega325P/3250P 118 Waveform D Generator D PORT ...

Page 119

... The timing diagram for the CTC mode is shown in increases until a compare match occurs with either OCR1A or ICR1, and then counter (TCNT1) is cleared. 8023F–AVR–07/09 ATmega325P/3250P 117.) ”Timer/Counter Timing Diagrams” on page Figure 15-6. The counter value (TCNT1) 126 ...

Page 120

... PWM modes that use dual-slope operation. This high frequency makes the fast PWM mode well suited for power regulation, rectification, and DAC applications. High frequency allows physically small sized external components (coils, capaci- tors), hence reduces total system cost. ATmega325P/3250P 120 1 2 ...

Page 121

... The OCR1A Register however, is double buffered. This feature allows the OCR1A I/O location 8023F–AVR–07/09 ( TOP log R = ---------------------------------- - FPWM log ATmega325P/3250P ) + Figure 15-7. The figure OCRnx / TOP Update and TOVn Interrupt Flag Set and OCnA Interrupt Flag Set or ICFn Interrupt Flag Set (Interrupt on TOP) (COMnx1 (COMnx1 ...

Page 122

... However, due to the symmetric feature of the dual-slope PWM modes, these modes are preferred for motor control applications. The PWM resolution for the phase correct PWM mode can be fixed to 8-, 9-, or 10-bit, or defined by either ICR1 or OCR1A. The minimum resolution allowed is 2-bit (ICR1 or OCR1A set to ATmega325P/3250P 122 Table 15-3 on page f ...

Page 123

... TOP actively while the Timer/Counter is running in the phase correct mode can result in an unsymmetrical output. The reason for this can be found in the time of update of the OCR1x Reg- ister. Since the OCR1x update occurs at TOP, the PWM period starts and ends at TOP. This 8023F–AVR–07/09 ATmega325P/3250P ( ) TOP ...

Page 124

... OCR1x Register is updated by the OCR1x Buffer Register, (see 8 and Figure The PWM resolution for the phase and frequency correct PWM mode can be defined by either ICR1 or OCR1A. The minimum resolution allowed is 2-bit (ICR1 or OCR1A set to 0x0003), and ATmega325P/3250P 124 f OCnxPCPWM 15-9). Table 1 on page ...

Page 125

... R = ---------------------------------- - PFCPWM Figure 15-9. The figure shows phase and frequency correct shows the output generated is, in contrast to the phase correct mode, symmetri- ATmega325P/3250P ( ) TOP + log OCnA Interrupt Flag Set or ICFn Interrupt Flag Set (Interrupt on TOP) OCRnx/TOP Updateand ...

Page 126

... The figures include information on when Interrupt Flags are set, and when the OCR1x Register is updated with the OCR1x buffer value (only for modes utilizing double buffering). Figure 15-10. Timer/Counter Timing Diagram, Setting of OCF1x, no Prescaling (clk TCNTn OCRnx OCFnx Figure 15-11 ATmega325P/3250P 126 f OCnxPFCPWM Figure 15-10 clk I/O clk Tn ...

Page 127

... FPWM) TCNTn TOP - 1 TOVn (FPWM) and ICFn (if used as TOP) OCRnx Old OCRnx Value (Update at TOP) shows the same timing data, but with the prescaler enabled. ATmega325P/3250P OCRnx OCRnx + 1 OCRnx Value TOP BOTTOM TOP TOP - 1 New OCRnx Value /8) clk_I/O OCRnx + 2 ...

Page 128

... OC1A or OC1B pin must be set in order to enable the output driver. When the OC1A or OC1B is connected to the pin, the function of the COM1x1:0 bits is depen- dent of the WGM13:0 bits setting. WGM13:0 bits are set to a Normal or a CTC mode (non-PWM). Table 15-2. COM1A1/COM1B1 ATmega325P/3250P 128 clk I/O clk Tn ...

Page 129

... A special case occurs when OCR1A/OCR1B equals TOP and COM1A1/COM1B1 is set. Section “15.9.4” on page 122. for more details. Table 15-14 on page ATmega325P/3250P (1) Description Normal port operation, OC1A/OC1B disconnected. WGM13 15: Toggle OC1A on Compare Match, OC1B disconnected (normal port operation). For all other WGM1 settings, normal port operation, OC1A/OC1B disconnected ...

Page 130

... When a capture is triggered according to the ICES1 setting, the counter value is copied into the Input Capture Register (ICR1). The event will also set the Input Capture Flag (ICF1), and this can be used to cause an Input Capture Interrupt, if this interrupt is enabled. ATmega325P/3250P 130 (1) WGM10 ...

Page 131

... I External clock source on T1 pin. Clock on falling edge External clock source on T1 pin. Clock on rising edge FOC1A FOC1B – R/W R ATmega325P/3250P – – – – Figure 0 – TCCR1C ...

Page 132

... The Output Compare Registers are 16-bit in size. To ensure that both the high and low bytes are written simultaneously when the CPU writes to these registers, the access is performed using an 8-bit temporary High Byte Register (TEMP). This temporary register is shared by all the other 16-bit registers. ATmega325P/3250P 132 7 6 ...

Page 133

... ICF1 Flag, located in TIFR1, is set. (See Section “11.” on page (See Section “11.” on page 53.) is executed when the TOV1 Flag, located in TIFR1, is set – – ICF1 ATmega325P/3250P ICR1[15:8] ICR1[7:0] R/W R/W R/W R ...

Page 134

... TOV1 Flag is set when the timer overflows. Refer to Flag behavior when using another WGM13:0 bit setting. TOV1 is automatically cleared when the Timer/Counter1 Overflow Interrupt Vector is executed. Alternatively, TOV1 can be cleared by writing a logic one to its bit location. ATmega325P/3250P 134 Table 15-14 on page 130 for the TOV1 ...

Page 135

... Control Logic direction BOTTOM TOP Timer/Counter TCNTn = 0 = 0xFF = OCRnx Synchronized Status flags Status flags ASSRn asynchronous mode select (ASn) ATmega325P/3250P Figure 16-1. For the actual placement 2. CPU accessible I/O Registers, including TOVn (Int.Req.) clk Tn TOSC1 T/C Oscillator Prescaler TOSC2 clk OCnx I/O (Int.Req.) Waveform ...

Page 136

... ASSR Register is written to logic one, the clock source is taken from the Timer/Counter Oscillator connected to TOSC1 and TOSC2. For details on asynchronous operation, see – Asynchronous Status Register” on page ”Timer/Counter Prescaler” on page ATmega325P/3250P 136 ). T2 for details. The compare match event will also set the Compare Flag (OCF2A) Table 16-1 are also used extensively throughout the section ...

Page 137

... Signalizes that TCNT2 has reached maximum value. Signalizes that TCNT2 has reached minimum value (zero). ). clk can be generated from an external or internal clock source present or not. A CPU write overrides (has priority over) all counter clear or T2 140. ATmega325P/3250P TOVn (Int.Req.) T/C clk Tn Oscillator Prescaler clk ...

Page 138

... All CPU write operations to the TCNT2 Register will block any compare match that occurs in the next timer clock cycle, even when the timer is stopped. This feature allows OCR2A to be initial- ized to the same value as TCNT2 without triggering an interrupt when the Timer/Counter clock is enabled. ATmega325P/3250P 138 140). shows a block diagram of the Output Compare unit. ...

Page 139

... PORT) that are affected by the COM2A1:0 bits are shown. When referring to the OC2A state, the reference is for the internal OC2A Register, not the OC2A pin. Figure 16-4. Compare Match Output Unit, Schematic COMnx1 COMnx0 FOCnx 8023F–AVR–07/09 Waveform Generator clk I/O ATmega325P/3250P Figure 16 OCnx PORT D ...

Page 140

... The Output Compare unit can be used to generate interrupts at some given time. Using the Out- put Compare to generate waveforms in Normal mode is not recommended, since this will occupy too much of the CPU time. ATmega325P/3250P 140 ”Register Description” on page Table 16-3 on page 150, and for phase correct PWM refer to (See Section “ ...

Page 141

... As for the Normal mode of operation, the counter counts from MAX to 0x00. 8023F–AVR–07/09 Figure clk_I ------------------------------------------------- - OCnx ⋅ ⋅ OCRnx 1 Flag is set in the same timer clock cycle that the TOV2 ATmega325P/3250P 16-5. The counter value (TCNT2) OCnx Interrupt Flag Set (COMnx1 OC2A ) = 141 ...

Page 142

... The PWM waveform is generated by setting (or clearing) the OC2A Register at the compare match between OCR2A and TCNT2, and clearing (or setting) the OC2A Register at the timer clock cycle the counter is cleared (changes from MAX to BOTTOM). ATmega325P/3250P 142 Figure 16-6. The TCNT2 value is in the timing diagram shown as a his- ...

Page 143

... The TCNT2 value is in the timing diagram shown as a histogram for illustrating the dual-slope operation. The diagram includes non-inverted and inverted PWM outputs. The small horizontal line marks on the TCNT2 slopes represent compare matches between OCR2A and TCNT2. 8023F–AVR–07/09 ATmega325P/3250P f clk_I/O f ...

Page 144

... Compare Match. The point of this transition is to guarantee symmetry around BOT- TOM. There are two cases that give a transition without Compare Match. • OCR2A changes its value from MAX, like in OCn pin value is the same as the result of a down-counting compare match. To ensure ATmega325P/3250P 144 1 2 ...

Page 145

... TCNTn MAX - 1 TOVn shows the same timing data, but with the prescaler enabled. clk I/O clk Tn (clk /8) I/O TCNTn MAX - 1 TOVn shows the setting of OCF2A in all modes except CTC mode. ATmega325P/3250P should be replaced by I/O MAX BOTTOM BOTTOM + 1 /8) clk_I/O MAX BOTTOM BOTTOM + 145 ...

Page 146

... Figure 16-10. Timer/Counter Timing Diagram, Setting of OCF2A, with Prescaler (f (clk TCNTn Figure 16-11 Figure 16-11. Timer/Counter Timing Diagram, Clear Timer on Compare Match mode, with Pres- (clk TCNTn ATmega325P/3250P 146 clk I/O clk Tn /8) I/O OCRnx - 1 OCRnx OCRnx OCFnx shows the setting of OCF2A and the clearing of TCNT2 in CTC mode. ...

Page 147

... Timer/Counter2 after power-up or wake-up from Power-down or Standby mode. The contents of all Timer/Counter2 Registers must be considered lost after a wake-up from Power-down or Standby mode due to unstable clock signal upon start-up, no matter whether the Oscillator is in use or a clock signal is applied to the TOSC1 pin. 8023F–AVR–07/09 ATmega325P/3250P 147 ...

Page 148

... The clock source for Timer/Counter2 is named clk system I/O clock clk clocked from the TOSC1 pin. This enables use of Timer/Counter2 as a Real Time Counter (RTC). When AS2 is set, pins TOSC1 and TOSC2 are disconnected from Port C. A crystal can ATmega325P/3250P 148 clk clk ...

Page 149

... CTC 1 1 Fast PWM 1. The CTC2 and PWM2 bit definition names are now obsolete. Use the WGM21:0 definitions. However, the functionality and location of these bits are compatible with previous versions of the timer. ATmega325P/3250P /8, clk T2S as well as 0 (stop) may be selected. T2S 4 3 ...

Page 150

... Note: Table 16-5 rect PWM mode. Table 16-5. COM2A1 Note: ATmega325P/3250P 150 Table 16-3 shows the COM2A1:0 bit functionality when the WGM21:0 bits Compare Output Mode, non-PWM Mode COM2A0 Description 0 Normal port operation, OC2A disconnected. 1 Toggle OC2A on compare match. 0 Clear OC2A on compare match. ...

Page 151

... OCR2A[7:0] R/W R/W R/W R – – – EXCLK R ATmega325P/3250P /(No prescaling) /8 (From prescaler) /32 (From prescaler) /64 (From prescaler) /128 (From prescaler) /256 (From prescaler) /1024 (From prescaler R/W R/W R/W R R/W R/W R/W R ...

Page 152

... When the OCIE2A bit is written to one and the I-bit in the Status Register is set (one), the Timer/Counter2 Compare Match A interrupt is enabled. The corresponding interrupt is executed if a compare match in Timer/Counter2 occurs, i.e., when the OCF2A bit is set in the Timer/Coun- ter 2 Interrupt Flag Register – TIFR2. ATmega325P/3250P 152 7 6 ...

Page 153

... TSM – – – R for a description of the Timer/Counter Synchronization mode. ATmega325P/3250P – – OCF2A TOV2 R R R/W R – – PSR2 PSR10 R R R/W R ...

Page 154

... Double Speed (CK/2) Master SPI Mode 17.2 Overview The Serial Peripheral Interface (SPI) allows high-speed synchronous data transfer between the ATmega325P/3250P and peripheral devices or between several AVR devices. A simplified block diagram of the Serial Peripheral Interface is shown in The PRSPI bit in enable the SPI module. ...

Page 155

... In SPI Slave mode, the control logic will sample the incoming signal of the SCK pin. To ensure correct sampling of the clock signal, the minimum low and high period should be: Low period: longer than 2 CPU clock cycles. High period: longer than 2 CPU clock cycles. ATmega325P/3250P 155 Figure 17-2 on page SHIFT ENABLE 8023F– ...

Page 156

... SPI Pin Overrides Direction, Master SPI User Defined Input User Defined User Defined 1. See ”Alternate Functions of Port B” on page 71 direction of the user defined SPI pins. ATmega325P/3250P ”Alternate Port Direction, Slave SPI Input User Defined Input Input for a detailed description of how to define the 156 ...

Page 157

... Enable SPI, Master, set clock rate fck/16 */ SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR0); } void SPI_MasterTransmit(char cData Start transmission */ SPDR = cData; /* Wait for transmission complete */ while(!(SPSR & (1<<SPIF))) } Note: ATmega325P/3250P 157 (1) r17,(1<<DD_MOSI)|(1<<DD_SCK) DDR_SPI,r17 r17,(1<<SPE)|(1<<MSTR)|(1<<SPR0) SPCR,r17 SPDR,r16 ( See Section “5.” on page 10. ...

Page 158

... SPI_SlaveReceive ; Read received data and return in r16,SPDR ret (1) /* Set MISO output, all others input */ DDR_SPI = (1<<DD_MISO); /* Enable SPI */ SPCR = (1<<SPE); /* Wait for reception complete */ while(!(SPSR & (1<<SPIF))) ; /* Return Data Register */ return SPDR; 1. See Section “5.” on page 10. ATmega325P/3250P 158 ...

Page 159

... This is clearly seen by summarizing Table 17-2 Table 3. CPOL Functionality CPOL=0, CPHA=0 CPOL=0, CPHA=1 CPOL=1, CPHA=0 CPOL=1, CPHA=1 ATmega325P/3250P 159 Figure 17-4. Data bits are shifted out and latched in on opposite edges of the SCK sig- and Table 17-3, as done below: ...

Page 160

... CHANGE 0 MISO PIN SS MSB first (DORD = 0) MSB Bit 6 LSB first (DORD = 1) LSB Bit SPIE SPE DORD MSTR R/W R/W R/W R ATmega325P/3250P Bit 4 Bit 3 Bit 2 Bit 1 Bit 3 Bit 4 Bit 5 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 2 Bit 3 Bit 4 Bit 5 Bit ...

Page 161

... These two bits control the SCK rate of the device configured as a Master. SPR1 and SPR0 have no effect on the Slave. The relationship between SCK and the Oscillator Clock frequency f shown in the following table: Table 17-4. SPI2X ATmega325P/3250P 161 Figure 17-3 on page 160 CPOL Functionality CPOL ...

Page 162

... When this bit is written logic one the SPI speed (SCK Frequency) will be doubled when the SPI is in Master mode (see be two CPU clock periods. When the SPI is configured as Slave, the SPI is only guaranteed to work at f The SPI interface on the ATmega325P/3250P is also used for program memory and EEPROM downloading or uploading. See 17.5.3 SPDR – SPI Data Register ...

Page 163

... A simplified block diagram of the USART Transmitter is shown in accessible I/O Registers and I/O pins are shown in bold. The Power Reduction USART bit, PRUSART0 must be written to zero to enable USART0 module. 8023F–AVR–07/09 ATmega325P/3250P Figure 18-1 on page ”PRR – Power Reduction Register” on page 164. CPU 163 ...

Page 164

... Frame Error, Data OverRun and Parity Errors. 18.2.1 AVR USART vs. AVR UART – Compatibility The USART is fully compatible with the AVR UART regarding: • Bit locations inside all USART Registers. • Baud Rate Generation. ATmega325P/3250P 164 (1) UBRR[H:L] BAUD RATE GENERATOR UDR (Transmit) ...

Page 165

... UBRR fosc UBRR+1 Prescaling Down-Counter OSC Sync Edge Register Detector xcki XCK xcko Pin DDR_XCK UCPOL Transmitter clock (Internal Signal). Receiver base clock (Internal Signal). ATmega325P/3250P Figure 18-1) if the Buffer Registers are U2X / DDR_XCK txclk 1 UMSEL 1 rxclk 0 ...

Page 166

... UMSELn, U2Xn and DDR_XCK bits. Table 18-3 ing the UBRRn value for each mode of operation using an internally generated clock source. ATmega325P/3250P 166 Input from XCK pin (internal Signal). Used for synchronous slave Clock output to XCK pin (Internal Signal). Used for synchronous master operation ...

Page 167

... Baud rate (in bits per second, bps) System Oscillator clock frequency Contents of the UBRRnH and UBRRnL Registers, (0-4095) 187). Figure 18-2 for details. depends on the stability of the system clock source therefore recommended to osc ATmega325P/3250P Equation for Calculating UBRRn (1) f OSC UBRRn ( ) + ...

Page 168

... If enabled, the parity bit is inserted after the data bits, before the stop bits. When a complete frame is transmitted, it can be directly followed by a new frame, or the communication line can be set to an idle (high) state. Figure 18-5 optional. Figure 18-5. Frame Formats ATmega325P/3250P 168 UCPOL = 1 XCK RxD / TxD UCPOL = 0 ...

Page 169

... even n 1 – ⊕ odd n 1 – Parity bit using even parity even odd Parity bit using odd parity Data bit n of the character n ATmega325P/3250P … ⊕ ⊕ ⊕ ⊕ ⊕ … ⊕ ⊕ ⊕ ...

Page 170

... However, many applications use a fixed setting of the baud and control registers, and for these types of applications the initialization code can be placed directly in the main routine combined with initialization code for other I/O modules. ATmega325P/3250P 170 (1) UBRR0H, r17 UBRR0L, r16 r16, (1< ...

Page 171

... Wait for empty transmit buffer sbis UCSR0A,UDRE0 rjmp USART_Transmit ; Put data (r16) into buffer, sends the data out UDR0,r16 ret (1) /* Wait for empty transmit buffer */ while ( !( UCSR0A & (1<<UDRE0 Put data into buffer, sends the data */ UDR0 = data; 1. See Section “5.” on page 10. ATmega325P/3250P 171 ...

Page 172

... Transmit Complete (TXCn). Both flags can be used for generating interrupts. The Data Register Empty (UDREn) Flag indicates whether the transmit buffer is ready to receive new data. This bit is set when the transmit buffer is empty, and cleared when the transmit buffer ATmega325P/3250P 172 (1)(2) ...

Page 173

... Shift Register will be moved into the receive buffer. The receive buffer can then be read by reading the UDRn I/O location. The following code example shows a simple USART receive function based on polling of the Receive Complete (RXCn) Flag. When using frames with less than eight bits the most significant 8023F–AVR–07/09 ATmega325P/3250P 173 ...

Page 174

... Flags as well. Read status from UCSRnA, then data from UDRn. Reading the UDRn I/O location will change the state of the receive buffer FIFO and consequently the TXB8n, FEn, DORn and UPEn bits, which all are stored in the FIFO, will change. ATmega325P/3250P 174 (1) ...

Page 175

... Get status and 9th bit, then data */ /* from buffer */ status = UCSR0A; resh = UCSR0B; resl = UDRn error, return - status & (1<<FE0)|(1<<DOR0)|(1<<UPE0) ) return -1; /* Filter the 9th bit, then return */ resh = (resh >> 1) & 0x01; return ((resh << resl); 1. See Section “5.” on page 10. ATmega325P/3250P 175 ...

Page 176

... Check to be performed (odd or even) is selected by the UPMn0 bit. When enabled, the Parity Checker calculates the parity of the data bits in incoming frames and compares the result with the parity bit from the serial frame. The result of the check is stored in the receive buffer together ATmega325P/3250P 176 ”Parity Bit Calculation” on page 169 and ” ...

Page 177

... Normal mode, and eight times the baud rate for Double Speed mode. The hor- izontal arrows illustrate the synchronization variation due to the sampling process. Note the 8023F–AVR–07/09 (1) sbis UCSR0A, RXC0 ret in r16, UDR0 rjmp USART_Flush (1) unsigned char dummy; while ( UCSR0A & (1<<RXC0) ) dummy = UDR0; 1. See Section “5.” on page 10. ATmega325P/3250P Figure 18-6 177 ...

Page 178

... RxD pin. The recovery process is then repeated until a complete frame is received. Including the first stop bit. Note that the Receiver only uses the first stop bit of a frame. Figure 18-8 of the next frame. ATmega325P/3250P 178 RxD IDLE 0 ...

Page 179

... R is the ratio of the fastest incoming data rate that can be fast accepted in relation to the receiver baud rate. and Table 18-2 list the maximum receiver baud rate error that can be tolerated. Note ATmega325P/3250P STOP 1 (A) ( ...

Page 180

... If the Receiver is set up to receive frames that contain data bits, then the first stop bit indi- cates if the frame contains data or address information. If the Receiver is set up for frames with ATmega325P/3250P 180 Recommended Maximum Receiver Baud Rate Error for Normal Speed Mode ...

Page 181

... Do not use Read-Modify-Write instructions (SBI and CBI) to set or clear the MPCMn bit. The MPCMn bit shares the same I/O location as the TXCn Flag and this might accidentally be cleared when using SBI or CBI instructions. 8023F–AVR–07/09 ATmega325P/3250P 181 ...

Page 182

... The TXCn Flag bit is auto- matically cleared when a transmit complete interrupt is executed can be cleared by writing a one to its bit location. The TXCn Flag can generate a Transmit Complete interrupt (see description of the TXCIEn bit). ATmega325P/3250P 182 7 6 ...

Page 183

... RXCIEn bit is written to one, the Global Interrupt Flag in SREG is written to one and the RXCn bit in UCSRnA is set. 8023F–AVR–07/09 ”Multi-processor Communication Mode” on page RXCIEn TXCIEn UDRIEn RXENn R/W R/W R/W R ATmega325P/3250P 180 TXENn UCSZn2 RXB8n TXB8n R/W R UCSRnB 183 ...

Page 184

... Must be written before writing the low bits to UDRn. 18.10.4 UCSRnC – USART Control and Status Register n C Bit Read/Write Initial Value • Bit 6 – UMSELn: USART Mode Select This bit selects between asynchronous and synchronous mode of operation. Figure 18-9. UMSELn Bit Settings ATmega325P/3250P 184 – UMSELn UPMn1 ...

Page 185

... USBSn 0 1 UCSZn2 UCSZn1 ATmega325P/3250P Parity Mode Disabled Reserved Enabled, Even Parity Enabled, Odd Parity Stop Bit(s) 1-bit 2-bit UCSZn0 Character Size 0 5-bit 1 6-bit 0 7-bit 1 8-bit 0 Reserved 1 Reserved 0 Reserved 1 9-bit ...

Page 186

... Higher error ratings are acceptable, but the Receiver will have less noise resis- tance when the error ratings are high, especially for large serial frames (see Operational Range” on page ATmega325P/3250P 186 Transmitted Data Changed (Output UCPOLn ...

Page 187

... MHz osc U2Xn = 1 U2Xn = 0 Error UBRRn Error 0.2% 47 0.0% 0.2% 23 0.0% 0.2% 11 0.0% -3.5% 7 0.0% -7.0% 5 0.0% 8.5% 3 0.0% 8.5% 2 0.0% 8.5% 1 0.0% -18.6% 1 -25.0% 8.5% 0 0.0% – – – – – – 125 kbps 115.2 kbps ATmega325P/3250P f = 2.0000 MHz osc U2Xn = 1 U2Xn = 0 UBRRn Error UBRRn Error 95 0.0% 51 0.2% 47 0.0% 25 0.2% 23 0.0% 12 0.2% 15 0.0% 8 -3.5% 11 0.0% 6 -7.0% 7 0.0% 3 8.5% 5 0.0% 2 8.5% 3 0.0% 1 8.5% 2 0.0% 1 -18 ...

Page 188

... Max. 230.4 kbps 460.8 kbps 1. UBRR = 0, Error = 0.0% ATmega325P/3250P 188 f = 4.0000 MHz osc U2Xn = 0 U2Xn = 1 Error UBRRn Error UBRRn 0.0% 103 0.2% 207 0.0% 51 0.2% 103 0.0% 25 0.2% 51 0.0% 16 2.1% 34 0.0% 12 0.2% 25 0.0% 8 -3.5% 16 0.0% 6 -7. ...

Page 189

... U2Xn = 0 Error UBRRn Error UBRRn -0.1% 287 0.0% 0.2% 143 0.0% 0.2% 71 0.0% 0.6% 47 0.0% 0.2% 35 0.0% -0.8% 23 0.0% 0.2% 17 0.0% 2.1% 11 0.0% 0.2% 8 0.0% -3.5% 5 0.0% 8.5% 2 0.0% 0.0% 2 -7.8% 0.0% – – 0.0% – – 1 Mbps 691.2 kbps ATmega325P/3250P MHz f = 14.7456 MHz osc U2Xn = 1 U2Xn = 0 Error UBRRn Error 575 0.0% 383 0.0% 287 0.0% 191 0.0% 143 0.0% 95 0.0% 95 0.0% 63 0.0% 71 0.0% 47 0.0% 47 0.0% 31 0.0% 35 0.0% 23 0.0% 23 0.0% 15 0.0% 17 0.0% 11 0.0% 11 0.0% 7 ...

Page 190

... Max. 1 Mbps 1. UBRR = 0, Error = 0.0% ATmega325P/3250P 190 f = 18.4320 MHz osc U2Xn = 0 Error UBRRn Error UBRRn 0.0% 479 0.0% -0.1% 239 0.0% 0.2% 119 0.0% -0.1% 79 0.0% 0.2% 59 0.0% 0.6% 39 0.0% 0.2% 29 0.0% -0.8% 19 0.0% 0.2% 14 0.0% 2.1% 9 0.0% -3.5% 4 0.0% 0.0% 4 -7.8% 0.0% – – 0.0% – – ...

Page 191

... ATmega3250P” on page 2 ”Register Descriptions” on page USIDR 4-bit Counter 1 0 [1] USISR 2 USICR ATmega325P/3250P and ”Pinout ATmega325P” on page 199. (Output only) DO (Input/Open Drain) DI/SDA TIM0 COMP 0 (Input/Open Drain) USCK/SCL 1 CLOCK HOLD Two-wire Clock Control Unit 3. CPU 191 ...

Page 192

... The same clock also increments the USI’s 4-bit counter. The Counter Overflow (interrupt) Flag, or USIOIF, can therefore be used to determine when a transfer is completed. The clock is generated by the Master device software by toggling the USCK pin via the PORT Register or by writing a one to the USITC bit in USICR. ATmega325P/3250P 192 Bit7 Bit6 ...

Page 193

... (Figure 19-3), a bus transfer involves the following steps: sts USIDR,r16 ldi r16,(1<<USIOIF) sts USISR,r16 ldi r16,(1<<USIWM0)|(1<<USICS1)|(1<<USICLK)|(1<<USITC) sts USICR,r16 lds r16, USISR sbrs r16, USIOIF ATmega325P/3250P LSB LSB E 193 ...

Page 194

... The fourth and fifth instruction set Three-wire mode, positive edge Shift Register clock, count at USITC strobe, and toggle USCK. The loop is repeated 16 times. The following code demonstrates how to use the USI module as a SPI Master with maximum speed (f SPITransfer_Fast: ret ATmega325P/3250P 194 rjmp SPITransfer_loop lds r16,USIDR ...

Page 195

... Three-wire mode and positive edge Shift Register clock. The loop is repeated until the USI Counter Overflow Flag is set. 8023F–AVR–07/09 ldi r16,(1<<USIWM0)|(1<<USICS1) sts USICR,r16 sts USIDR,r16 ldi r16,(1<<USIOIF) sts USISR,r16 lds r16, USISR sbrs r16, USIOIF rjmp SlaveSPITransfer_loop lds r16,USIDR ret ATmega325P/3250P 195 ...

Page 196

... The clock is generated by the master by toggling the USCK pin via the PORT Register. The data direction is not given by the physical layer. A protocol, like the one used by the TWI- bus, must be implemented to control the data flow. ATmega325P/3250P 196 Bit7 Bit6 ...

Page 197

... Figure 19-6. Start Condition Detector, Logic Diagram 8023F–AVR–07/ ADDRESS R/W ACK (Figure 19-6) detects the start condition and sets the USISIF SDA SCL Write( USISIF) ATmega325P/3250P DATA ACK DATA ACK USISIF CLOCK HOLD CLR CLR P F ...

Page 198

... The Overflow Flag and Interrupt Enable bit are then used for the external interrupt. This feature is selected by the USICS1 bit. 19.4.5 Software Interrupt The counter overflow interrupt can be used as a software interrupt triggered by a clock strobe. ATmega325P/3250P 198 Figure 19-6 The SDA line is delayed (in the range of 50 ”Clock Systems and their Distribution” on page /4 ...

Page 199

... Idle sleep mode. 8023F–AVR–07/ MSB R/W R/W R/W R USISIF USIOIF USIPF USIDC R/W R/W R ATmega325P/3250P LSB R/W R/W R/W R USICNT3 USICNT2 USICNT1 USICNT0 R/W R/W R/W R USIDR ...

Page 200

... Data and clock inputs are not affected by the mode selected and will always have the same function. The counter and Shift Register can therefore be clocked exter- nally, and data input sampled, even when outputs are disabled. The relations between USIWM1:0 and the USI operation is summarized in ATmega325P/3250P 200 7 6 ...