ATTINY4313-MU Atmel, ATTINY4313-MU Datasheet - Page 30

• Manufacturer Part Number: ATTINY4313-MU
• Description: IC MCU AVR 4K FLASH 20QFN
• Manufacturer: Atmel
• Series: AVR® ATtinyr

Specifications of ATTINY4313-MU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 18
• Program Memory Size: 4KB (2K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 256 x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.5 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 20-VQFN Exposed Pad, 20-HVQFN, 20-SQFN, 20-DHVQFN
• Processor Series: ATtiny
• Core: AVR
• Data Bus Width: 8 bit
• Data Ram Size: 256 B
• Interface Type: SPI, USART, USI
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 18
• Number Of Timers: 2
• Operating Supply Voltage: 3.3 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Operating Temperature Range: - 40 C to + 85 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Data Converters: -
• Lead Free Status / Rohs Status: Details

6.4
6.5
6.5.1
6.5.2
30
Clock Output Buffer
Register Description
ATtiny2313A/4313
OSCCAL – Oscillator Calibration Register
CLKPR – Clock Prescale Register
The device can output the system clock on the CLKO pin. To enable the output, the CKOUT
fuse has to be programmed. This mode is suitable when the chip clock is used to drive other cir-
cuits on the system. Note that the clock will not be output during reset and that the normal
operation of the I/O pin will be overridden when the fuse is programmed. Any clock source,
including the internal RC Oscillator, can be selected when the clock is output on CLKO. If the
System Clock Prescaler is used, it is the divided system clock that is output.
• Bit 7 – Res: Reserved Bit
This bit is reserved bit in ATtiny2313A/4313 and it will always read zero.
• Bits 6:0 – CAL[6:0]: Oscillator Calibration Value
Writing the calibration byte to this address will trim the internal Oscillator to remove process vari-
ations from the Oscillator frequency. This is done automatically during Chip Reset. When
OSCCAL is zero, the lowest available frequency is chosen. Writing non-zero values to this regis-
ter will increase the frequency of the internal Oscillator. Writing 0x7F to the register gives the
highest available frequency.
The calibrated Oscillator is used to time EEPROM and Flash access. If EEPROM or Flash is
written, do not calibrate to more than 10% above the nominal frequency. Otherwise, the
EEPROM or Flash write may fail. Note that the Oscillator is intended for calibration to 8 MHz or 4
MHz. Tuning to other values is not guaranteed, as indicated in
To ensure stable operation of the MCU the calibration value should be changed in small steps. A
variation in frequency of more than 2% from one cycle to the next can lead to unpredicatble
behavior. Changes in OSCCAL should not exceed 0x20 for each calibration. It is required to
ensure that the MCU is kept in Reset during such changes in the clock frequency
Table 6-8.
• Bit 7 – CLKPCE: Clock Prescaler Change Enable
Bit
0x31 (0x51)
Read/Write
Initial Value
Bit
0x26 (0x46)
Read/Write
Initial Value
OSCCAL Value
0x3F
0x7F
0x00
Internal RC Oscillator Frequency Range
CLKPCE
R/W
R
7
–
0
7
0
with Respect to Nominal Frequency
CAL6
R/W
Typical Lowest Frequency
6
R
6
–
0
CAL5
R/W
5
100%
R
5
–
0
50%
75%
Device Specific Calibration Value
CAL4
R/W
4
R
4
–
0
CLKPS3
CAL3
R/W
R/W
3
3
with Respect to Nominal Frequency
CLKPS2
See Bit Description
CAL2
R/W
R/W
2
2
Table 6-8
Typical Highest Frequency
CLKPS1
CAL1
R/W
R/W
1
1
below.
100%
150%
200%
CLKPS0
CAL0
R/W
R/W
0
0
8246A–AVR–11/09
OSCCAL
CLKPR