ATmega128 datasheet(306/386 Pages) ATMEL

306 / 386 page

306

2467S–AVR–07/09

ATmega128

Figure 146. State Machine Sequence for Changing the Instruction Word

AVR_RESET ($C)

The AVR specific public JTAG instruction for setting the AVR device in the Reset mode or taking

the device out from the Reset mode. The TAP controller is not reset by this instruction. The one

bit Reset Register is selected as Data Register. Note that the reset will be active as long as there

is a logic 'one' in the Reset Chain. The output from this chain is not latched.

The active states are:

•

Shift-DR: The Reset Register is shifted by the TCK input.

PROG_ENABLE ($4)

The AVR specific public JTAG instruction for enabling programming via the JTAG port. The 16-

bit Programming Enable Register is selected as data register. The active states are the

following:

•

Shift-DR: the programming enable signature is shifted into the data register.

•

Update-DR: the programming enable signature is compared to the correct value, and

Programming mode is entered if the signature is valid.

Test-Logic-Reset

Run-Test/Idle

Shift-DR

Exit1-DR

Pause-DR

Exit2-DR

Update-DR

Select-IR Scan

Capture-IR

Shift-IR

Exit1-IR

Pause-IR

Exit2-IR

Update-IR

Select-DR Scan

Capture-DR

ATmega128 Datasheet(PDF) 306 Page - ATMEL Corporation