Debug Support
ARM DDI0145B
Copyright © 1998, 1999 ARM Limited. All rights reserved.
5-23
Scan chain 1
Purpose
Primarily for debugging, although it can be used for EXTEST on
the data data bus
DD[31:0]
and the instruction data bus
ID[31:0]
.
Scan chain 1 is selected via the SCAN_N TAP controller
instruction.
Length
67 bits.
This scan chain is 67 bits long, 32 bits for data values, 32 bits for instruction data, and
3 control bits, SYSSPEED, WPTANDBKPT, and
DDEN
. The three control bits serve
four different purposes:
•
Under normal INTEST test conditions, the
DDEN
signal can be captured and
examined.
•
During EXTEST test conditions, a known value can be scanned into
DDEN
to be
driven into the rest of the system. If a logic 1 is scanned into
DDEN
, the data data
bus
DD[31:0]
will drive out the values stored in its scan cells. If a logic 0 is
scanned into
DDEN
,
DD[31:0]
will capture the current input values.
•
While debugging, the value placed in the SYSSPEED control bit determines
whether the ARM9TDMI synchronizes back to system speed before executing
the instruction.
•
After the ARM9TDMI has entered debug state, the first time SYSSPEED is
captured and scanned out, its value tells the debugger whether the core has entered
debug state due to a breakpoint (SYSSPEED LOW), or a watchpoint
(SYSSPEED HIGH). If the instruction directly following one which causes a
watchpoint has a breakpoint set on it, then the WPT and BKPT bit will be set. This
situation does not affect how to restart the code.
Содержание ARM9TDMI
Страница 1: ...Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ARM9TDMI Technical Reference Manual ...
Страница 6: ...Contents vi Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...
Страница 12: ...Preface xii Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...
Страница 16: ...Introduction 1 4 Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...
Страница 22: ...Programmer s Model 2 6 Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...
Страница 36: ...ARM9TDMI Processor Core Memory Interface 3 14 Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...
Страница 54: ...ARM9TDMI Coprocessor Interface 4 18 Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...
Страница 110: ...Test Issues 6 6 Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...
Страница 138: ...ARM9TDMI AC Characteristics 8 20 Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...
Страница 150: ...ARM9TDMI Signal Descriptions A 12 Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...
Страница 154: ...Index Index 4 Copyright 1998 1999 ARM Limited All rights reserved ARM DDI0145B ...