GE 68K System - Manual (Page 47)

68K System Monitor
User's Guide
GE Energy Services
General SWM0023-1.00 -2
Full Release 3-21
DB - Define Breakpoint
Platform þ CPM þ D20
D20 Base o D20 ME
D20 Base o D20/200
CCU Base þ D20/200 ME
CCU Base þ D25
Description 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.
Syntax 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
Considerations You may define only one breakpoint at a single address, to a
maximum of ten breakpoints per system. An attempt to define
a breakpoint in read only or non-existent memory results in a
bus error.