![](http://datasheet.mmic.net.cn/30000/MR80C32-20-D_datasheet_2377239/MR80C32-20-D_233.png)
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
24.3.2.3
Manufacturer ID
The Manufacturer ID is a 11 bit code identifying the manufacturer. The JTAG manufacturer ID
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
“ClockMSB
LSB
Bit
31
28
271211
1
0
Device ID
Version
Part Number
Manufacturer ID
1
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