ATmega162 datasheet(250/324 Pages) ATMEL

250 / 324 page

250

2513K–AVR–07/09

ATmega162/V

Programming via

the JTAG Interface

Programming through the JTAG interface requires control of the four JTAG specific pins: TCK,

TMS, TDI, and TDO. Control of the Reset and clock pins is not required.

To be able to use the JTAG interface, the JTAGEN Fuse must be programmed. The device is

default shipped with the Fuse programmed. In addition, the JTD bit in MCUCSR must be

cleared. Alternatively, if the JTD bit is set, the External Reset can be forced low. Then, the JTD

bit will be cleared after two chip clocks, and the JTAG pins are available for programming. This

provides a means of using the JTAG pins as normal port pins in running mode while still allowing

In-System Programming via the JTAG interface. Note that this technique can not be used when

using the JTAG pins for Boundary-scan or On-chip Debug. In these cases the JTAG pins must

be dedicated for this purpose.

As a definition in this datasheet, the LSB is shifted in and out first of all Shift Registers.

Programming Specific

JTAG Instructions

The Instruction Register is 4-bit wide, supporting up to 16 instructions. The JTAG instructions

useful for Programming are listed below.

The OPCODE for each instruction is shown behind the instruction name in hex format. The text

describes which Data Register is selected as path between TDI and TDO for each instruction.

The Run-Test/Idle state of the TAP controller is used to generate internal clocks. It can also be

used as an idle state between JTAG sequences. The state machine sequence for changing the

instruction word is shown in Figure 107.

ATmega162 데이터시트(PDF) 250 Page - ATMEL Corporation