
Debug in depth
C-32
Copyright 2000 ARM Limited. All rights reserved.
ARM DDI 0165B
If bit 3 of the control register is programmed to 0, the comparators examine the
instruction address, instruction data, and instruction control buses. In this case bits [2]
and [0] of the mask register must be set to don’t care (programmed to 1_1). The format
of the register in this case is as shown in
Figure C-9.Figure C-9 Watchpoint control register for instruction comparison
6
CHAIN
Selects the chain output of another watchpoint unit in order to
implement some debugger requests. For example, breakpoint on
address YYY only when in process XXX.
In the ARM9E-S EmbeddedICE-RT logic, the CHAINOUT
output of watchpoint 1 is connected to the CHAIN input of
watchpoint 0. The CHAINOUT output is derived from a latch.
The address or control field comparator drives the write enable
for the latch and the input to the latch is the value of the data
field comparator. The CHAINOUT latch is cleared when the
control value register is written or when DBGnTRST is LOW.
7
RANGE
Can be connected to the range output of another watchpoint
register. In the ARM9E-S EmbeddedICE-RT logic, the address
comparator output of watchpoint 1 is connected to the RANGE
input of watchpoint 0. This allows you to couple two
watchpoints for detecting conditions that occur simultaneously,
for example, for range-checking.
8
ENABLE
If a watchpoint match occurs, the internal DWPT signal is only
asserted when the ENABLE bit is set. This bit only exists in the
value register. It cannot be masked.
Table C-5 Watchpoint control register for data comparison functions (continued)
Bit
number
Name
Function
765432
1
0
ENABLE
RANGE
CHAIN
DBGEXT InTRANS
0
X
ITBIT
8