
Debug in depth
ARM DDI 0165B
Copyright 2000 ARM Limited. All rights reserved.
C-33
Instruction comparison bit functions are described in
Table C-6..
Table C-6 Watchpoint control register for instruction comparison functions
Bit
number
Name
Function
1
ITBIT
Compares against the Thumb state signal from the core to
determine between a Thumb (ITBIT = 1) instruction fetch or an
ARM (ITBIT = 0) instruction fetch.
4
InTRANS
Compares against the not translate signal from the core in order to
determine between a user mode (InTRANS = 0) instruction fetch,
and a privileged mode (InTRANS = 1) fetch.
5
DBGEXT
Is an external input into the EmbeddedICE-RT logic that allows
the watchpoint to be dependent upon some external condition.
The DBGEXT input for watchpoint 0 is labelled DBGEXT[0],
and the DBGEXT input for watchpoint 1 is labeled DBGEXT[1].
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 nTRST 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 IBREAKPTsignal is
only asserted when the ENABLE bit is set. This bit only exists in
the value register, it cannot be masked.