Debug in Depth
B-14 Copyright © 2001, 2004 ARM Limited. All rights reserved. ARM DDI 0210C
B.6 Test data registers
There are seven test data registers that can connect between TDI and TDO:
• Bypass register
• ARM7TDMI core device IDentification (ID) code register
• Instruction register on page B-15
• Scan path select register on page B-15
• Scan chains 0, 1, 2, and 3 on page B-16.
In the following test data register descriptions, data is shifted during every TCK cycle.
B.6.1 Bypass register
Purpose Bypasses the device during scan testing by providing a path
between TDI and TDO.
Length 1 bit.
Operating mode When the BYPASS instruction is the current instruction in the
instruction register, serial data is transferred from TDI to TDO in
the SHIFT-DR state with a delay of one TCK cycle. There is no
parallel output from the bypass register.
A 0 is loaded from the parallel input of the bypass register in the
CAPTURE-DR state.
B.6.2 ARM7TDMI core device IDentification (ID) code register
Purpose Reads the 32-bit device identification code. No programmable
supplementary identification code is provided.
Length 32 bits. The format of the register is as shown in Figure B-3.
Figure B-3 ID code register format
10
31 28 27 12 11 1 0
1 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1
Version Part number Manufacturer identity
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