ATMEGA2561V ATMEL [ATMEL Corporation], ATMEGA2561V Datasheet - Page 309

• Manufacturer Part Number: ATMEGA2561V
• Description: 8-bit Microcontroller with 64K/128K/256K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Bypass Register
Device Identification Register
Version
Part Number
Manufacturer ID
Reset Register
2549K–AVR–01/07
The Bypass Register consists of a single Shift Register stage. When the Bypass Regis-
ter 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 130 shows the structure of the Device Identification Register.
Figure 130. 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
ATmega640/1280/1281/2560/2561 is listed in Table 154 on page 345.
The Manufacturer ID is a 11-bit code identifying the manufacturer. The JTAG manufac-
turer ID for ATMEL is listed in Table 154 on page 345.
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 settings for the clock options, the part will remain reset for a reset time-out
period (see “Clock Sources” on page 39) after releasing the Reset Register. The output
from this Data Register is not latched, so the reset will take place immediately, as shown
in Figure 131.
Figure 131. Reset Register
Bit
Device ID
From Other Internal and
External Reset Sources
MSB
31
Version
4 bits
28
From
ClockDR · AVR_RESET
TDI
ATmega640/1280/1281/2560/2561
27
Part Number
16 bits
D
Q
TDO
To
12
11
Manufacturer ID
11 bits
Internal reset
1
LSB
1-bit
1
0
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