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NAME
BKPT -- Break-point
SYNOPSIS
BKPT #<data>
FUNCTION
This instruction is used to support the program breakpoint
function for debug monitors and real-time hardware emulators, and
the operation will be dependent on the implementation. Execution of
this instruction will cause the MC68010 to run a breakpoint
acknowledge bus cycle and zeros on all address lines, but an
MC68020 will place the immediate data on lines A2, A3, and A4, and
zeros on lines A0 and A1.
Whether the breakpoint acknowledge cycle is terminaled with
_____ ____ ___
(DTACK), (BERR), or (VPA) the processor always takes an illegal
instruction exception. During exception processing, a debug monitor
can distinguish eight different software breakpoints by decoding the
field in the BKPT instruction.
For the MC68000 and the MC68HC000, this instruction causes an illegal
instruction exception, but does not run the breakpoint acknowledge
bus cycle.
There are two possible responses on an MC68020: normal and exception.
The normal response is an operation word (typically the instruction
______
the BKPT originally replaced) on the data lines with the (DSACKx)
signal asserted. The operation word is the executed in place of the
breakpoint instruction.
For the exception response, a bus error signal will cause the MC68020
to take an illegal instruction exception, just as an MC68010 or
MC68000 would do.
FORMAT
-----------------------------------------------------------------
|15 |14 |13 |12 |11 |10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|-----------|
| 0 | 1 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 |N° BREAKPT.|
-----------------------------------------------------------------
Number of break-point: Value between 0 and 7.
RESULT
None.
SEE ALSO
ILLEGAL