Rockwell Automation 1771-DB Basic Module User Manual - Series A - Manual (Page 126)

Operating Functions
Chapter 5
5–89
The user is now executing ROM 4 if it exists. If the ROM routine
requested does not exist the result is:
PROGRAM NOT FOUND.
READY
u
This routine allows you to return to the ROM or RAM routine that called
this ROM or RAM routine. Execution begins on the line following the line
that CALLed the routine. No arguments are PUSHed or POPed. This
routine works one layer deep. You may go back to the last CALLing
program’s next line.
Important: There must be a next line in the ROM or RAM routine,
otherwise unpredictable events could occur which may destroy the
contents of RAM. For this reason always be sure that at least one END
statement exists following a Call 70 or 71.
Example:
uROM #1
u10 REM SAMPLE PROG FOR CALL 72
u20 PRINT “NOW EXECUTING ROM #1
u30 PUSH
3
u40 CALL 71 :REM EXECUTE ROM #3 THEN RETURN
u50 PRINT “EXECUTING ROM #1 AGAIN”
u60 END
ROM #3
u10 REM THIS LINE WONT BE EXECUTED
u20 PRINT “NOW EXECUTING ROM #3”
u30 CALL
72
u40 END
With ROM #1 selected:
uRUN
NOW EXECUTING ROM #1
NOW EXECUTING ROM #3
EXECUTING ROM #1 AGAIN
READY
u
5.11.2
ROM/RAM to ROM Program
Transfer – CALL 71
(continued)
5.11.3
RAM/ROM Return – CALL 72