Debug in Depth
ARM DDI 0210C
Copyright © 2001, 2004 ARM Limited. All rights reserved.
B-11
B.5.5
CLAMP (b0101)
This instruction connects a single-bit shift register, the BYPASS register, between
TDI
and
TDO
. When the CLAMP instruction is loaded into the instruction register, the state
of all the scan cell output signals is defined by the values previously loaded into the
currently loaded scan chain. This instruction must only be used when scan chain 0 is the
currently selected scan chain:
•
In the CAPTURE-DR state, a 0 is captured by the bypass register.
•
In the SHIFT-DR state, test data is shifted into the bypass register using
TDI
and
out using
TDO
after a delay of one
TCK
cycle. The first bit shifted out is a 0.
•
In the UPDATE-DR state the bypass register is not affected.
B.5.6
HIGHZ (b0111)
This instruction connects a single-bit shift register, the BYPASS register, between
TDI
and
TDO
. When the HIGHZ instruction is loaded into the instruction register, the
Address bus,
A[31:0]
, the data bus,
D[31:0]
,
nRW
,
nOPC
,
LOCK
,
MAS[1:0]
, and
nTRANS
are all driven to the high impedance state and the external
HIGHZ
signal is
driven HIGH. This is as if the signal
TBE
had been driven LOW:
•
In the CAPTURE-DR state, a 0 is captured by the bypass register.
•
In the SHIFT-DR state, test data is shifted into the bypass register using
TDI
and
out using
TDO
after a delay of one
TCK
cycle. The first bit shifted out is a 0.
•
In the UPDATE-DR state, the bypass register is not affected.
B.5.7
CLAMPZ (b1001)
This instruction connects a single-bit shift register, the BYPASS register, between
TDI
and
TDO
.
When the CLAMPZ instruction is loaded into the instruction register, all the tristate
outputs are placed in their inactive state, but the data supplied to the scan cell outputs is
derived from the scan cells. The purpose of this instruction is to ensure that, during
production test, each output can be disabled when its data value is either 0 or 1:
•
In the CAPTURE-DR state, a 0 is captured by the bypass register.
•
In the SHIFT-DR state, test data is shifted into the bypass register using
TDI
and
out using
TDO
after a delay of one
TCK
cycle. The first bit shifted out is a 0.
•
In the UPDATE-DR state, the bypass register is not affected.
Summary of Contents for ARM7TDMI
Page 6: ...Contents vi Copyright 2001 2004 ARM Limited All rights reserved ARM DDI 0210C ...
Page 10: ...List of Tables x Copyright 2001 2004 ARM Limited All rights reserved ARM DDI 0210C ...
Page 14: ...List of Figures xiv Copyright 2001 2004 ARM Limited All rights reserved ARM DDI 0210C ...
Page 46: ...Introduction 1 26 Copyright 2001 2004 ARM Limited All rights reserved ARM DDI 0210C ...
Page 120: ...Coprocessor Interface 4 18 Copyright 2001 2004 ARM Limited All rights reserved ARM DDI 0210C ...
Page 142: ...Debug Interface 5 22 Copyright 2001 2004 ARM Limited All rights reserved ARM DDI 0210C ...
Page 282: ...Glossary Glossary 6 Copyright 2001 2004 ARM Limited All rights reserved ARM DDI 0210C ...