Lakeshore Learning Materials 622 Uživatelský manuál stáhnout pdf (Strana 47)

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"

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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