ATmega16A datasheet(233/352 Pages) ATMEL

233 / 352 page

233

8154B–AVR–07/09

ATmega16A

24.3.1

Bypass Register

The Bypass Register consists of a single Shift Register stage. When the Bypass Register is

selected as path between TDI and TDO, the register is reset to 0 when leaving the Capture-DR

controller state. The Bypass Register can be used to shorten the scan chain on a system when

the other devices are to be tested.

24.3.2

Device Identification Register

Figure 24-1 shows the structure of the Device Identification Register.

Figure 24-1. The Format of the Device Identification Register

24.3.2.1

Version

Version is a 4-bit number identifying the revision of the component. The JTAG version number

follows the revision of the device. Revision A is 0x0, revision B is 0x1 and so on. However, some

revisions deviate from this rule, and the relevant version number is shown in Table 24-1.

24.3.2.2

Part Number

The part number is a 16-bit code identifying the component. The JTAG Part Number for

ATmega16A is listed in Table 24-2.

24.3.2.3

Manufacturer ID

The Manufacturer ID is a 11 bit code identifying the manufacturer. The JTAG manufacturer ID

for ATMEL is listed in Table 24-3.

24.3.3

Reset Register

The Reset Register is a Test Data Register used to reset the part. Since the AVR tri-states Port

Pins when reset, the Reset Register can also replace the function of the unimplemented optional

JTAG instruction HIGHZ.

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 set-

tings for the clock options, the part will remain reset for a Reset Time-Out Period (refer to “Clock

MSB

LSB

Bit

271211

Device ID

Version

Part Number

Manufacturer ID

4 bits

16 bits

11 bits

1 bit

Table 24-1.

JTAG Version Numbers

Version

JTAG Version Number (Hex)

ATmega16A revision TBD

TBD

Table 24-2.

AVR JTAG Part Number

Part Number

JTAG Part Number (Hex)

ATmega16A

0x9403

Table 24-3.

Manufacturer ID

Manufacturer

JTAG Manufacturer ID (Hex)

ATMEL

0x01F

ATmega16A Datasheet(PDF) 233 Page - ATMEL Corporation

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