Motorola CPU32 Bedienungsanleitung PDF herunterladen (Seite 157)

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Integer Instructions

MOTOROLA M68000 FAMILY PROGRAMMER’S REFERENCE MANUAL 4-53

BKPT Breakpoint BKPT

(MC68EC000, MC68010, MC68020, MC68030, MC68040, CPU32)

Operation: Run Breakpoint Acknowledge Cycle; TRAP As Illegal Instruction

Assembler

Syntax: BKPT # < data >

Attributes: Unsized

Description: For the MC68010, a breakpoint acknowledge bus cycle is run with function

codes driven high and zeros on all address lines. Whether the breakpoint acknowledge

bus cycle is terminated with DT

ACK, BERR, or VPA, the processor always takes an

illegal instruction exception. During exception processing, a debug monitor can

distinguish different software breakpoints by decoding the ﬁeld in the BKPT instruction.

For the MC68000 and MC68008, the breakpoint cycle is not run, but an illegal

instruction exception is taken.

For the MC68020, MC68030, and CPU32, a breakpoint acknowledge bus cycle is exe-

cuted with the immediate data (value 0 – 7) on bits 2 – 4 of the address bus and zeros

on bits 0 and 1 of the address bus. The breakpoint acknowledge bus cycle accesses

the CPU space, addressing type 0, and provides the breakpoint number specified by

the instruction on address lines A2 – A4. If the external hardware terminates the cycle

with DSACKx

or STERM, the data on the bus (an instruction word) is inserted into the

instruction pipe and is executed after the breakpoint instruction. The breakpoint instruc-

tion requires a word to be transferred so, if the first bus cycle accesses an 8- bit port,

a second bus cycle is required. If the external logic terminates the breakpoint acknowl-

edge bus cycle with BERR

(i.e., no instruction word available), the processor takes an

illegal instruction exception.

For the MC68040, this instruction executes a breakpoint acknowledge bus cycle.

Regardless of the cycle termination, the MC68040 takes an illegal instruction excep-

tion.

For more information on the breakpoint instruction refer to the appropriate user’s man-

ual on bus operation.

This instruction supports breakpoints for debug monitors and real- time hardware emu-

lators.

1 2 ... 152 153 154 155 156 157 158 159 160 161 162 ... 645 646

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