Status Instruments DM4000U, Manual

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The following basic program provides an example of a simple communications
interface to run on a PC. The program is coded to use COM1 and communicate with
device 1, but these may be modified as required.
10 OPEN ``COM1:9600,N,8,1'' AS #1: header$=''01''
20 INPUT ``Enter text string ( 0 to quit)'';text$:if text$=''0'' goto 90
50 gosub 100: PRINT#1,TX$
70 gosub 200: if left$(text$,1) = `'!'' then mid$(text$,1,1)= `'?'':goto 50
80 print ``RECEIVED[ `';rx$;'' ]'': goto 20
90 end
100 REM Calculates block check character based on header and text strings
150 sum=0: lh=len(header$):lt=len(text$)
170 for i=1 to lh:sum=sum+asc(mid$(header$,i,1)):next
180 for i=1 to lt:sum=sum+asc(mid$(text$,i,1)):next:bcc=sum-(256*int(sum/256))
190tx$=chr$(1)+chr$(2)+text$+chr$(3)+chr$(bcc)
195 return
200 REM Reads in received data without checking block check character
240 rx$=''''
245 ch$ = input$(1,#1):if ch$ <> chr$(1) goto 245
250 ch$ = input$(1,#1):if ch$ <> chr$(2) goto 250
260 ch$ = input$(1,#1):if ch$ = chr$(3) goto 270
265 rx$=rx$+ch$:goto 260
270 return
The following tables list the available comms mnemonics for the instrument.
RATE IN ENGINEERING UNITS
APPENDIX E
APPENDICES
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