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6 ERRORS DURING RS-422-A OUTPUT
6.1 Preventing Errors
Chapter 6 ERRORS DURING RS-422-
A OUTPUT
6.1 Preventing Errors
Do not send an FM or LF command from the host PC until the measured data or set
point data in all the channels specified by the last command have been output. If an FM
or LF command is sent while the VR200 recorder is outputting data, a communication
error may occur.
An LF command sent after the TS0 command, or an FM command sent after the TS1 or
TS2 command may also cause a communication error.
If an ESC T command was already sent after the last time TS0 was set, data (even in
other formats) in any channel at any time interval can be read by the host PC using FM
commands as many times as required. At this time (when the FM command is
repeatedly sent), the VR200 recorder also sends the data acquired last time ESC T was
received.
Also, if an ESC T command was already sent after the last time TS1 or TS2 was set, the
settings (even in other formats) in any channel at any time interval can be read by the
host PC using LF commands as many times as required.
Thus, once the ESC T command has been sent, the measured values and set values can
be read any number of times, which is a very useful function.
Note
When sending data from the host PC to a recorder, use the ESC S command to avoid buffer overflow:
When the VR200 recorder receives an ESC S request, it saves it in the buffer memory. This request is retrieved from the buffer
memory and, after acknowledging the command, the recorder sends the status to the PC. Make sure not to send any other
commands between sending the ESC S command to the recorder and reading the status from the recorder. This ensures that
commands can be received by the recorder since its input buffer is empty.
Example:
10 OPEN ”COM1:N81N” AS #1
20 ‘
30 PRINT #1,CHR$(&H1B)+”O 01"
40 PRINT #1,”SR01,VOLT,20mV,-2000,2000"
50 GOSUB *HANDSHAKE
60 PRINT #1,”PS0"
70 GOSUB *HANDSHAKE
80 PRINT #1,”UD0"
90 PRINT #1,CHR$(&H1B)+”C 01"
100 CLOSE
110 END
120 *HANDSHAKE
130 PRINT #1,CHR$(&H1B)+”S”; (sending ESC S)
140 LINE INPUT #1,STS$ (reading status)
150 RETURN
The command length of the input buffer of the VR200 is 256 bytes for a 4-channel model.