"display" in three flavors:
Add the expression expr to the list of expressions to display each time your program stops. See section Expressions.
display does not repeat if you press RET again after using it.
For fmt specifying only a display format and not a size or count, add the expression expr to the auto-display list but arrange to display it each time in the specified format fmt. See section Output Formats.
For fmt `i' or `s', or including a unit-size or a number of units, add the expression addr as a memory address to be examined each time your program stops. Examining means in effect doing `x/fmt addr'. See section Examining Memory.
Example for the 3rd usage:
This is useful to examine a 16-bit register
2. /proc/devices: show the major number
root:/> cat /proc/devices
3. About Trace Buffer
Blackfin records every program sequence change in trace buffer, if trace buffer is enabled. There is a 16-entry TBUF register table.
- A bit (TBUGOVF) in the TB control register can enable exception when the TBUF overflows (>16 entry). In the exception handler, TBUF can be read into memory, so that we can record more than 16 traces.
- The trace buffer can be configured to omit the recording of changes in program flow that match either the last entry or one of the last two entries.
- If TBUFOVF = 1, then the Trace Unit does not record discontinuities in the exception, NMI, and reset routines, because TB itself triggers exception.
- Setting TBUFOVF have impact on performance - every 16 sequence change would trigger an exception.
Wednesday, June 24, 2009
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