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7.2.3
Breakpoints and watchpoints
Breakpoints
A breakpoint stops the core when a selected instruction is executed. It is then possi-
ble to examine the contents of both memory and variables.
Watchpoints (called data breakpoints)
A watchpoint stops the core if a selected memory location is accessed. For a watch-
point (WP), the following properties can be specified:
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Address (including address mask)
Type of access (R, R/W, W)
Data (including data mask)
Software / hardware breakpoints
Hardware breakpoints are real breakpoints. Hardware breakpoints can be set in any
type of memory (RAM, ROM, flash) and also work with self-modifyingcode. Unfortu-
nately, there is only a limited number of hardware breakpoints available. When
debugging a program located in RAM, another option is to use software breakpoints.
With software breakpoints, the instruction in memory is modified. This does not work
when debugging programs located in ROM or flash, but has one huge advantage: the
number of software breakpoints is not limited.
The debug module provides a number of hardware resources to support various hard-
ware breakpoint functions. Specifically, three types of breakpoints are supported:
PC with mask, operand address range, and data with mask.These three basic break-
points can be configured into one- or two-level triggers with the exact trigger
response also programmable. The debug module programming model is accessible
from either the external development system using the serial interface or from the
processor ’s supervisor programming model using the WDEBUG instruction.
J-Link ColdFire BDM 26 (UM08009)
? 2004-2009 SEGGER Microcontroller GmbH & Co. KG