Fluke 5820A, Operator'S Manual

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5820A
Operators Manual
5-48
5-63. Using the RS-232 UUT Port to Control an instrument
The SERIAL 2 TO UUT RS-232 port is used to pass commands on to another instrument.
For example, a meter that is being calibrated can have its RS-232 port connected the
calibrator SERIAL 2 TO UUT serial port. Commands sent from a controller can be
routed through the calibrator’s UUT port and received by the meter or UUT. There are
six special
UUT_* commands incorporated into the calibrator for passing commands on
to an instrument connected to the UUT port. Refer to Chapter 6 for more information.
5-64. Input Buffer Operation
As the 5820A Calibrator receives each data byte from the controller, it places the bytes in
a portion of memory called the input buffer. The input buffer holds up to 350 data bytes
and operates in a first in, first out fashion.
IEEE-488 The 5820A 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) when it has read enough of the input buffer so that it is less than
40 % full. When using RTS (Request to Send) protocol (selected as part of the “RS-232
Host Port Setup Procedure”), the serial interface asserts and unasserts RTS in response to
same conditions as for XON/XOFF protocol.