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Remote Operation
4
Checking 525B Status
IEEE-488 The Calibrator treats the EOI IEEE-488 control line as a separate data
byte and inserts it into the input buffer if it is encountered as part of a message
terminator. Input buffer operation is transparent to the program running on the
controller. If the controller sends commands faster than the Calibrator can process
them, the input buffer fills to capacity. When the input buffer is full, the Calibrator
holds off the IEEE-488 bus with the NRFD (Not Ready For Data) handshake line.
When the Calibrator has processed a data byte from the full input buffer, it then
completes the handshake, allowing the controller to send another data byte. The
calibrator clears the input buffer on power-up and on receiving the DCL (Device
Clear) or SDC (Selected Device Clear) messages from the controller.
RS-232 Under RS-232-C serial port remote control using ^S (<Cntl> S) XOFF
protocol, the Calibrator issues a ^S XOFF when the input buffer becomes 80%
full. The calibrator issues a ^Q (<Cntl> Q) XON when it has read enough of the
input buffer so that it is less than 40% full.
4-27
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