ATMEGA64L-8MI View Datasheet(PDF) - Atmel Corporation

Part Name

Description

Manufacturer

ATMEGA64L-8MI

8-bit AVR® Microcontroller with 64K Bytes In-System Programmable Flash

Atmel Corporation 

ATmega64(L)

Data Registers

The data registers are selected by the JTAG instruction registers described in section

“Programming Specific JTAG Instructions” on page 312. The data registers relevant for

programming operations are:

• Reset Register

• Programming Enable Register

• Programming Command Register

• Virtual Flash Page Load Register

• Virtual Flash Page Read Register

Reset Register

The Reset Register is a Test Data Register used to reset the part during programming. It

is required to reset the part before entering programming mode.

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 36) 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 126 on page 256.

Programming Enable Register

The Programming Enable Register is a 16-bit register. The contents of this register is

compared to the programming enable signature, binary code 1010_0011_0111_0000.

When the contents of the register is equal to the programming enable signature, pro-

gramming via the JTAG port is enabled. The register is reset to 0 on Power-on Reset,

and should always be reset when leaving Programming mode.

Figure 150. Programming Enable Register

TDI

D

A

$A370

=

T

A

D

Q

Programming Enable

ClockDR & PROG_ENABLE

TDO

2490G–AVR–03/04

315

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