Remote Processing BASIC 52 - Manual (Page 147)

RPBASIC-52 PROGRAMMING GUIDE
A-3
rem if last two digits don't sum to message, then return a negative
rem acknowledge error and bail out
1170 if oc <> ocksum then $(2) = "N2" : goto 1510
rem Checksum is good
REM If status command, go process it
1200 IF oa = 4 THEN 4000
1210 if oa > 5 then 1500
:REM if not in command, is error
REM Check for valid power up acknowledge
REM if not acknowledged, then state so
1220 if oflag = 0 then $(2) = "N3" : goto 1510
rem process command
rem GOSUB's could also be used here. However, goto's are faster as
rem exiting the routine makes a direct branch to the condition
rem Cmdn letter A B C D E F
1240 on oa goto 2000,2500,3000,3500,4000,4500
rem If more commands, check for limit. If over, then subtract command
rem and make another ON GOTO
REM Common return point for successful completion of a command
REM Return acknowledge to sender.
REM Used for commands
1400 $(2)="A"
1410 GOTO 1510 :REM to common output & exit
REM Return negative acknowledge to sender.
REM N1 = unrecognized command
REM N2 = checksum bad
REM N3 = power up not acknowledged. Needs command 5.
REM N4 = bad data
REM N5 = something is wrong. Can add error conditions as needed
1500 $(2)="N1"
1510 rem UO1
1520 PRINT $(2)
rem 1530 UO0 :REM back to main port
1540 RETURN
REM convert ASCII HEX number into a number 0 - 15
REM Enter with oc = ASCII value of number (0-9 or A-F which is 48-
REM 58 or 65 to 70)
REM If problem, oc returns -1. If OK, returns number 0 to 15
1600 if (oc < 48) .or. (oc > 70) then oc = -1 : return
1610 if oc > 58 then 1640
rem value between 0 and 9. Simply subtract 48 and exit
1620 oc = oc-48
1630 return
rem Value should be between A-F
1640 if oc < 65 then oc = -1 : return
1650 oc = oc - 55
1660 return
REM Send back acknowledge