
B-8
Detailed Debug Operation
Rev. A
Copyright 2000 by LSI Logic Corporation. All rights reserved.
B.4.2 INTEST (1100)
The INTEST instruction places the selected scan chain in test mode:
The INTEST instruction connects the selected scan chain between
DBGTDI and DBGTDO.
When the INTEST instruction is loaded into the Instruction Register,
all the scan cells are placed in their test mode of operation.
In the CAPTURE-DR state, the value of the data applied from the
core logic to the output scan cells and the value of the data applied
from the system logic to the input scan cells are captured.
In the SHIFT-DR state, the previously captured test data is shifted out
of the scan chain via the DBGTDO pin, while new test data is shifted
in via the DBGTDI pin.
Single-step operation of the core is possible using the INTEST
instruction.
B.4.3 IDCODE (1110)
The IDCODE instruction connects the device identification code register
(or ID register) between DBGTDI and DBGTDO. The ID register is a 32-
bit register that allows the manufacturer, part number, and version of a
component to be read through the TAP. See
Section B.5.2, “ARM7TDMI-
S Device Identification (ID) Code Register,”
for the details of the ID
register format.
When the IDCODE instruction is loaded into the Instruction Register, all
the scan cells are placed in their normal (system) mode of operation:
In the CAPTURE-DR state, the ID register captures the device
identification code.
In the SHIFT-DR state, the previously captured device identification
code is shifted out of the ID register via the DBGTDO pin, while data
is shifted into the ID register via the DBGTDI pin.
In the UPDATE-DR state, the ID register is unaffected.