ATMEGA640 datasheet(344/436 Pages) MICROCHIP

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ATmega640/V-1280/V-1281/V-2560/V-2561/V [DATASHEET]

DS40002211A

30.9.2

AVR_RESET (0xC)

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

30.9.3

PROG_ENABLE (0x4)

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

30.9.4

PROG_COMMANDS (0x5)

The AVR specific public JTAG instruction for entering programming commands via the JTAG port. The 15-bit Pro-

gramming Command Register is selected as Data Register. The active states are the following:

•

Capture-DR: The result of the previous command is loaded into the Data Register

•

Shift-DR: The Data Register is shifted by the TCK input, shifting out the result of the previous command and

shifting in the new command

•

Update-DR: The programming command is applied to the Flash inputs

•

Run-Test/Idle: One clock cycle is generated, executing the applied command

30.9.5

PROG_PAGELOAD (0x6)

The AVR specific public JTAG instruction to directly load the Flash data page via the JTAG port. An 8-bit Flash

Data Byte Register is selected as the Data Register. This is physically the 8 LSBs of the Programming Command

•

Shift-DR: The Flash Data Byte Register is shifted by the TCK input.

•

Update-DR: The content of the Flash Data Byte Register is copied into a temporary register. A write sequence

is initiated that within 11 TCK cycles loads the content of the temporary register into the Flash page buffer. The

AVR automatically alternates between writing the low and the high byte for each new Update-DR state, starting

with the low byte for the first Update-DR encountered after entering the PROG_PAGELOAD command. The

Program Counter is pre-incremented before writing the low byte, except for the first written byte. This ensures

that the first data is written to the address set up by PROG_COMMANDS, and loading the last location in the

page buffer does not make the program counter increment into the next page.

30.9.6

PROG_PAGEREAD (0x7)

The AVR specific public JTAG instruction to directly capture the Flash content via the JTAG port. An 8-bit Flash

Data Byte Register is selected as the Data Register. This is physically the 8 LSBs of the Programming Command

•

Capture-DR: The content of the selected Flash byte is captured into the Flash Data Byte Register. The AVR

automatically alternates between reading the low and the high byte for each new Capture-DR state, starting

with the low byte for the first Capture-DR encountered after entering the PROG_PAGEREAD command. The

Program Counter is post-incremented after reading each high byte, including the first read byte. This ensures

that the first data is captured from the first address set up by PROG_COMMANDS, and reading the last

location in the page makes the program counter increment into the next page.

•

Shift-DR: The Flash Data Byte Register is shifted by the TCK input.

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