ATmega162 datasheet(253/324 Pages) ATMEL

253 / 324 page

253

2513K–AVR–07/09

ATmega162/V

Data Registers

The Data Registers are selected by the JTAG Instruction Registers described in section “Pro-

gramming Specific JTAG Instructions” on page 250. 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 86 on page 206.

Programming Enable

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, programming 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 108. Programming Enable Register

TDI

TDO

ClockDR & PROG_ENABLE

Programming Enable

0xA370

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