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BKPT
Operation:
Assembler
Syntax:
Attributes:
Breakpoint
Run breakpoint acknowledge cycle;
If acknowledged
then execute returned operation word
else TRAP as illegal instruction
BKPT #(data)
Unsized
BKPT
Description:
Executes a breakpoint acknowledge bus cycle. Bits [2:4] of the address bus are set to
the value of the immediate data (0 to 7) and bits 0 and 1 of the address bus are set to O.
The breakpoint acknowledge cycle accesses the CPU space, addressing type 0, and provides
the breakpoint number
s~ecified
by the instruction on address lines A4 to A2. If external hardware
terminates the cycle with DSACKxx, the data on the bus (an instruction word) is inserted into the
instruction pipe and is executed after the breakpoint instruction. The breakpoint instruction
requires a word transfer - if the first bus cycle accesses an 8-bit port, a second cycle is required. If
III
external logic terminates the breakpoint acknowledge cycle with BERR (Le., no instruction word
•
available) the processor takes an illegal instruction exception. Refer to 7.2.5 Software
Breakpoints for details of breakpoint operation.
This instruction supports breakpoints for debug monitors and real-time hardware emulators. The
exact operation performed by the instruction is implementation-dependent. Typically, this
instruction replaces an instruction in a program and the replaced instruction is returned by the
breakpoint acknowledge cycle.
Condition Codes:
Not affected.
Instruction Format:
15
14
13
12
11
10
9
8
7
6
5
4
3
2 1 0
0 0 0
0
o
o
o
I
o
o
I
1
VECTOR
Instruction Fields:
Vector field - Contains immediate data in the range (0-7). This is the breakpoint number.
CPU32 REFERENCE MANUAL
INSTRUCTION SET
MOTOROLA
4-47
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