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Information in this article applies to:

  • C251 Version 2.14


We are trying to use Mon251 V2 on our design with an 80C251G1D-16BI. We generated a ROM monitor at adress 01E800h. The ROM monitor starts running well. When we are in "Record trace" mode, "step by step" and "break point" all work as expected but execution time is too slow.

When "record trace" is off, execution speed is correct but we can't activate the "step by step" and break point" functions.

Is this normal?


Yes and No...

The reason that the trace is slow is because the monitor has to send 20 bytes of information to the PC for each instruction that is executed. At 9600 baud (1000 cps approx.) that is only 50 instructions per second. That's pretty slow!!!

Single-step and break-points work whether or not trace is enabled. If you can't single-step, something else must be wrong. Make sure you don't try to step over instructions that modify the stack pointer (since the monitor uses the stack, too).

You may want to check the configuration to ensure that serial break is enabled. That lets you stop execution by clicking on the STOP button.

Last Reviewed: Wednesday, November 16, 2005

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