ARM ARM7TDMI User Manual Page 122

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Debugging Your System
5-18 Copyright © 2001 ARM Limited. All rights reserved. ARM DDI 0234B
5.9 Monitor mode debugging
The ARM7TDMI-S (Rev 4) processor contains logic that enables the debugging of a
system without stopping the core entirely. This means that critical interrupt routines
continue to be serviced while the core is being interrogated by the debugger.
5.9.1 Enabling monitor mode
The debugging mode is controlled by bit 4 of the debug control register (described in
Debug control register on page 5-57). Bit 4 of this register is also known as the monitor
mode enable bit:
Bit 4 set Enables the monitor mode features of the ARM7TDMI-S processor.
When this bit is set, the EmbeddedICE-RT logic is configured so that a
breakpoint or watchpoint causes the ARM7TDMI-S core to enter abort
mode, taking the Prefetch or Data Abort vectors respectively.
Bit 4 clear Monitor mode debugging is disabled and the system is placed into halt
mode. In halt mode, the core enters debug state when it encounters a
breakpoint or watchpoint.
5.9.2 Restrictions on monitor-mode debugging
There are several restrictions you must be aware of when the ARM core is configured
for monitor-mode debugging:
Breakpoints and watchpoints cannot be data-dependent in monitor mode. No
support is provided for use of the range functionality. Breakpoints and
watchpoints can only be based on the following:
instruction or data addresses
external watchpoint conditioner (DBGEXT[0] or DBGEXT[1])
User or privileged mode access (CPnTRANS)
read/write access for watchpoints (WRITE)
access size (watchpoints SIZE[1:0]).
External breakpoints or watchpoints are not supported.
No support is provided to mix halt mode and monitor mode functionality.
The fact that an abort has been generated by the monitor mode is recorded in the abort
status register in coprocessor 14 (see Abort status register on page 5-56).
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