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Chapter 6 errors during rs-422- a output, 1 preventing errors – Omega Speaker Systems VR200 User Manual

Page 33

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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.