68HC12 stepper bug

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In systems with a co-resident monitor program (Dbug-12, MON12, etc), the
single-stepper data stack pointer is being corrupted by the monitor's
exception handler. It is necessary to retrieve the data stack pointer from
the SWI exception frame before accessing the stack. The SWI exception
handler <+DEBUG> should look like this:

LABEL <+DEBUG>
   5 ,SP LDY \ Get data stack pointer from exception
frame
   2 ,-Y STS \ Return stack address
   7 ,SP 2 ,-Y MOVW \ Address of next word to execute
   STEPPING # 2 ,-Y MOVW \ Single-step indicator
   CLI ' BREAKPOINT JSR \ Return control to host
   END-CODE \ Continue in <-DEBUG>

This will be corrected in the next maintenance release.

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Received on Wed Jan 22 2003 - 09:32:13 PST