Lake Shore Model 620/622/623/647 Magnet Power Supply User’s Manual
Remote Operation
4-9
4.2.4 Notes On Using The Serial Interface
• To chain commands together, insert a semi-colon (;) between them. Multiple queries cannot be chained.
• Queries use the same syntax as the associated setting command followed by a question mark (?). They
usually return the same information that is sent.
• Add a query to the end of a command string if the controller must return information. For example, RMP
0;RMP? commands the MPS to pause the ramp then return the ramp status to confirm the change.
• The MPS returns nothing queries without a “?" and ignores misspelled commands and queries.
• The term "free field" indicates a floating decimal point that can be placed at any appropriate place in the
string of digits.
• Leading zeros and zeros following a decimal point are unneeded in a command string, but they are sent in
response to a query. A leading “+” is not required, but a leading “–”
is required.
• [term] indicates where the user places terminating characters or where they appear on a returning character
string from the MPS.
Table 4-3. Sample BASIC Serial Interface Program
' SEREXAM.BAS EXAMPLE PROGRAM FOR SERIAL INTERFACE
' This program works with QuickBasic 4.0/4.5 or Qbasic on an IBM PC or compatible
' with a serial interface. It uses the COM1 communication port at 9600 BAUD. Enter
' an instrument command or query at the prompt. The command transmits to the
' instrument which displays any query response. Type "EXIT" to exit the program.
' NOTE: The INPUT instruction in this example accepts no commas as part of an input
' string. If a comma appears in an instrument command, replace it with a space.
'
CLS 'Clear screen
PRINT " SERIAL COMMUNICATION PROGRAM"
PRINT
TIMEOUT = 2000 'Read timeout (may need more)
BAUD$ = "9600"
TERM$ = CHR$(13) + CHR$(10) 'Terminators are <CR><LF>
OPEN "COM1:" + BAUD$ + ",N,8,1,RS" FOR RANDOM AS #1 LEN = 256
LOOP1: INPUT "ENTER COMMAND (or EXIT):"; CMD$ 'Get command from keyboard
CMD$ = UCASE$(CMD$) 'Change input to upper case
IF CMD$ = "EXIT" THEN CLOSE #1: END 'Get out on Exit
CMD$ = CMD$ + TERM$
PRINT #1, CMD$; 'Send command to instrument
IF INSTR(CMD$, "?") <> 0 THEN 'Test for query
RS$ = "" 'If query, read response
N = 0 'Clr return string and count
WHILE (N < TIMEOUT) AND (INSTR(RS$, TERM$) = 0) 'Wait for response
IN$ = INPUT$(LOC(1), #1) 'Get one character at a time
IFIN$=""THENN=N+1ELSEN=0'Add 1 to timeout if no chr
RS$ = RS$ + IN$ 'Add next chr to string
WEND 'Get chrs until terminators
IF RS$ <> "" THEN 'See if return string is empty
RS$ = MID$(RS$, 1, (INSTR(RS$, TERM$) - 1)) 'Strip off terminators
PRINT "RESPONSE:"; RS$ 'Print response to query
ELSE
PRINT "NO RESPONSE" 'No response to query
END IF
END IF 'Get next command
GOTO LOOP1
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