2 restrictions on monitor-mode debugging – Epson ARM.POWERED ARM720T User Manual

Page 145

9: Debugging Your System

ARM720T CORE CPU MANUAL

EPSON

9-13

9.9.2

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 (HWRITE)

–

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

The monitor mode enable bit does not put the ARM720T processor into debug state. For this

reason, it is necessary to change the contents of the watchpoint registers while external

memory accesses are taking place, rather than changing them when in debug state where the

core is halted.
If there is a possibility of false matches occurring during changes to the watchpoint registers

(caused by old data in some registers and new data in others) you must:

Disable the watchpoint unit by setting bit 5 in the Debug Control Register (also

known as the EmbeddedICE-RT disable bit).

Poll the Debug Control Register until the EmbeddedICE-RT disable bit is read back

as set.

Change the other registers.

Re-enable the watchpoint unit by clearing the EmbeddedICE-RT disable bit in the

Debug Control Register.

See

on page 9-39 for more information about controlling core behavior

at breakpoints and watchpoints.