68K System Monitor

User's Guide

GE Energy Services

DB - Define Breakpoint

Platform

Description

Syntax

þ CPM þ D20

o D20 ME

o D20/200

þ D20/200 ME

þ D25

D20 Base

D20 Base

CCU Base

CCU Base

 

Use this command to activate a breakpoint in a section of code located within RAM.

At the specified address, the command saves 68000 family instruction in the breakpoint table and replaces it with a TRAP instruction. When a process reaches the TRAP instruction, it traps into a breakpoint handling routine, which displays a message indicating that it encountered a breakpoint.

The 68K Monitor allows up to ten active breakpoints.

Below is usage and syntax information for this command

Command Format

db address [#loops]

 

 

 

 

Variables

None

 

 

 

 

 

 

Parameters

address

=

hexadecimal address for the breakpoint.

 

#loops

=

number of times to execute the specified address

 

 

 

(in decimal) before stopping; default is zero

 

 

 

 

 

Example

Type db 103648 and press ENTER.

 

 

 

This defines a breakpoint at hexadecimal address 103648,

 

 

 

which stops before the first execution of the instruction at that

 

 

 

address.

 

 

 

Results: The system responds with the breakpoint number

 

 

 

assigned to this breakpoint and the prompt. Each time

 

 

 

it encounters the breakpoint, the system displays the

 

 

 

breakpoint number, loop count, and register values. If

 

 

 

the loop count is greater than zero, it is decremented.

 

 

 

Otherwise, the process is suspended.

 

 

 

 

 

 

Special

You may define only one breakpoint at a single address, to a

 

 

Considerations

maximum of ten breakpoints per system. An attempt to define

 

 

 

a breakpoint in read only or non-existent memory results in a

 

 

 

bus error.

 

 

 

 

 

 

 

 

 

General

SWM0023-1.00 -2

Full Release

3-21

 

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GE 68K System manual DB Define Breakpoint