Rainbow Electronics ATmega3290P_V - Manual (Page 243)

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ATmega329/3290/649/6490
2552H–AVR–11/06
Bypass Register 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.
Device Identification Register Figure 108 shows the structure of the Device Identification Register.
Figure 108. The Format of the Device Identification Register
Version 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.
Part Number The part number is a 16-bit code identifying the component. The JTAG Part Number for
ATmega329/3290/649/6490 is listed in Table 107.
Manufacturer ID The Manufacturer ID is a 11-bit code identifying the manufacturer. The JTAG manufac-
turer ID for ATMEL is listed in Table 108.
Reset Register 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 109.
MSB LSB
Bit 31 28 27 12 11 1 0
Device ID Version Part Number Manufacturer ID 1
4 bits 16 bits 11 bits 1-bit
Table 107. AVR JTAG Part Number
Part Number JTAG Part Number (Hex)
ATmega329 0x9503
ATmega3290 0x9504
ATmega649 0x9603
ATmega6490 0x9604
Table 108. Manufacturer ID
Manufacturer JTAG Manufacturer ID (Hex)
ATMEL 0x01F