Rainbow Electronics ATmega128L - Manual (Page 245)

245
ATmega128(L)
2467B–09/01
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 121 shows the structure of the Device Identification register.
Figure 121. The Format of the Device Identification Register
•
Version
Version is a 4 bit number identifying the revision of the component. The relevant version
number is shown in
Table 99.
•
Part Number
The part number is a 16 bit code identifying the component. The JTAG Part Number for
ATmega128 is listed in
Table 100.
•
Manufacturer ID
The Manufacturer ID is a 11-bit code identifying the manufacturer. The JTAG manufac-
turer ID for ATMEL is listed in
Table 101.
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 34) 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 122.
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 99. JTAG Version Numbers
Version JTAG Version number (Hex)
ATmega128 revision C 0x3
Table 100. AVR JTAG Part Number
Part number JTAG Part Number (Hex)
ATmega128 0x9702
Table 101. Manufacturer ID
Manufacturer JTAG Man. ID (Hex)
ATMEL 0x01F