ATtiny85 Atmel Corporation, ATtiny85 Datasheet - Page 144

• Manufacturer Part Number: ATtiny85
• Manufacturer: Atmel Corporation

Specifications of ATtiny85

• Flash (kbytes): 8 Kbytes
• Pin Count: 8
• Max. Operating Frequency: 20 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 3
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 6
• Ext Interrupts: 6
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Twi (i2c): 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 4
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 0.5
• Eeprom (bytes): 512
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8 to 5.5
• Operating Voltage (vcc): 1.8 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 2
• Output Compare Channels: 5
• Pwm Channels: 6
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

18.4
18.5
18.6
18.6.1
144
Software Break Points
Limitations of debugWIRE
Register Description
ATtiny25/45/85
DWDR – debugWire Data Register
When designing a system where debugWIRE will be used, the following must be observed:
debugWIRE supports Program memory Break Points by the AVR Break instruction. Setting a
Break Point in AVR Studio
tion replaced by the BREAK instruction will be stored. When program execution is continued, the
stored instruction will be executed before continuing from the Program memory. A break can be
inserted manually by putting the BREAK instruction in the program.
The Flash must be re-programmed each time a Break Point is changed. This is automatically
handled by AVR Studio through the debugWIRE interface. The use of Break Points will therefore
reduce the Flash Data retention. Devices used for debugging purposes should not be shipped to
end customers.
The debugWIRE communication pin (dW) is physically located on the same pin as External
Reset (RESET). An External Reset source is therefore not supported when the debugWIRE is
enabled.
The debugWIRE system accurately emulates all I/O functions when running at full speed, i.e.,
when the program in the CPU is running. When the CPU is stopped, care must be taken while
accessing some of the I/O Registers via the debugger (AVR Studio). See the debugWIRE docu-
mentation for detailed description of the limitations.
The debugWIRE interface is asynchronous, which means that the debugger needs to synchro-
nize to the system clock. If the system clock is changed by software (e.g. by writing CLKPS bits)
communication via debugWIRE may fail. Also, clock frequencies below 100kHz may cause com-
munication problems.
A programmed DWEN Fuse enables some parts of the clock system to be running in all sleep
modes. This will increase the power consumption while in sleep. Thus, the DWEN Fuse should
be disabled when debugWire is not used.
The following section describes the registers used with the debugWire.
The DWDR Register provides a communication channel from the running program in the MCU
to the debugger. This register is only accessible by the debugWIRE and can therefore not be
used as a general purpose register in the normal operations.
Bit
0x22
Read/Write
Initial Value
• Pull-Up resistor on the dW/(RESET) line must be in the range of 10k to 20 kΩ. However, the
• Connecting the RESET pin directly to V
• Capacitors inserted on the RESET pin must be disconnected when using debugWire.
• All external reset sources must be disconnected.
pull-up resistor is optional.
DWDR7
R/W
7
0
DWDR6
R/W
®
6
0
will insert a BREAK instruction in the Program memory. The instruc-
DWDR5
R/W
5
0
DWDR4
CC
R/W
4
0
will not work.
DWDR3
R/W
3
0
DWDR2
R/W
2
0
DWDR1
R/W
1
0
DWDR0
R/W
0
0
2586N–AVR–04/11
DWDR