ATMEGA644P-20PQ Atmel, ATMEGA644P-20PQ Datasheet - Page 267

• Manufacturer Part Number: ATMEGA644P-20PQ
• Description: MCU AVR 64K FLASH 20MHZ 40-PDIP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA644P-20PQ

• 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: 32
• Program Memory Size: 64KB (32K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 2K x 8
• Ram Size: 4K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 40-DIP (0.600", 15.24mm)
• For Use With: ATSTK600 - DEV KIT FOR AVR/AVR32
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

22.3
22.3.1
22.3.2
Version
Part Number
Manufacturer ID
22.3.3
8011O–AVR–07/10
Data Registers
Bypass Register
Device Identification Register
Reset Register
The Data Registers relevant for Boundary-scan operations are:
• Bypass Register
• Device Identification Register
• Reset Register
• Boundary-scan Chain
The Bypass Register consists of a single Shift Register stage. When the Bypass Register is
selected as path between TDI and TDO, the register is reset to 0 when leaving the Capture-DR
controller state. The Bypass Register can be used to shorten the scan chain on a system when
the other devices are to be tested.
Figure 22-1
Figure 22-1. The Format of the Device Identification Register
Version is a 4-bit number identifying the revision of the component. The JTAG version number
follows the revision of the device. Revision A is 0x0, revision B is 0x1 and so on.
The part number is a 16-bit code identifying the component. The JTAG Part Number for
ATmega164P/324P/644P is listed in
The Manufacturer ID is a 11-bit code identifying the manufacturer. The JTAG manufacturer ID
for ATMEL is listed in
The Reset Register is a test Data Register used to reset the part. Since the AVR tri-states Port
Pins when reset, the Reset Register can also replace the function of the unimplemented optional
JTAG instruction HIGHZ.
A high value in the Reset Register corresponds to pulling the external Reset low. The part is
reset as long as there is a high value present in the Reset Register. Depending on the fuse set-
tings for the clock options, the part will remain reset for a reset time-out period (refer to
Sources” on page
not latched, so the reset will take place immediately, as shown in
Bit
Device ID
shows the structure of the Device Identification Register.
MSB
31
Version
4 bits
30) after releasing the Reset Register. The output from this Data Register is
Table 24-6 on page
28
27
Table 24-6 on page
Part Number
16 bits
296.
ATmega164P/324P/644P
296.
12
11
Figure
Manufacturer ID
11 bits
22-2.
1
LSB
1-bit
”Clock
1
0
267