ATMEGA325-16AJ ATMEL [ATMEL Corporation], ATMEGA325-16AJ Datasheet - Page 217

• Manufacturer Part Number: ATMEGA325-16AJ
• Description: 8-bit Microcontroller with In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Bypass Register
Device Identification Register
Version
Part Number
Manufacturer ID
Reset Register
2570A–AVR–09/04
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 99 shows the structure of the Device Identification Register.
Figure 99. 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
ATmega325/3250/645/6450 is listed in Table 91.
Table 91. AVR JTAG Part Number
The Manufacturer ID is a 11-bit code identifying the manufacturer. The JTAG manufac-
turer ID for ATMEL is listed in Table 92.
Table 92. Manufacturer ID
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 (refer to “Clock Sources” on page 26) after releasing the Reset Register. The out-
put from this Data Register is not latched, so the reset will take place immediately, as
shown in Figure 100.
Bit
Device ID
Part Number
ATmega325
ATmega3250
ATmega645
ATmega6450
Manufacturer
ATMEL
MSB
31
Version
4 bits
28
27
Part Number
ATmega325/3250/645/6450
16 bits
JTAG Manufacturer ID (Hex)
JTAG Part Number (Hex)
12
11
0x9503
0x9504
0x9603
0x9604
Manufacturer ID
0x01F
11 bits
1
LSB
1-bit
1
0
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