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Incoming Character Processing
The 5730A Calibrator processes all incoming data as follows (except the 8-bit data byte
portion of the *PUD parameter):
1. An eighth bit (DIO8) is ignored.
2. All data is taken as 7-bit ASCII.
3. Lower-case or upper-case characters are accepted.
4. ASCII characters whose decimal equivalent is less than 32 (Space) are discarded,
except for characters 10 (LF) and 13 (CR) and in the *PUD command argument.
*PUD allows all characters in its argument and terminates in a special way.
Response Message Syntax
In Table 6-5, responses from the 5730A Calibrator are described wherever appropriate. In
order to know whether to read in an integer, a floating-point number, or character string,
the first entry is (Integer), (Floating), or (String).
The responses described in the command tables are correct for IEEE-488
remote control, and for serial/Ethernet/USB remote control in COMPUTER
mode. TERMINAL mode (in serial/Ethernet/USB remote control),
responses contain more descriptive text intended for an operator using a
terminal interactively.
Integers for most controllers or computers are decimal numbers in the range -32768 to
32767. Response elements of this type are labeled as "integer" in the command tables.
Floating-point numbers may be in exponential form, for example "1.15E-12". String
responses may be any ASCII printing characters. A special case of string response is in
the CAL_CLST?, CAL_SHIFT?, CAL_SLST?, CAL_RPT?, ECHO?, EXPLAIN?,
RPT_STR?, *OPT?, and *STATE? commands. Those strings include leading and
trailing quotation marks. (See Table 5-2 for details.)
Input Buffer Operation
As the 5730A 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 128 data bytes
and operates in a first in, first out fashion.
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.
Under RS-232C serial port remote control that uses Control/S (XOFF) protocol, the
Calibrator issues a Control/S (XOFF) when the input buffer becomes 80 % full. The
Calibrator issues a Control/Q (XON) when it has read enough of the input buffer so that it
is less than 40 % full. When RTS (Request to Send) protocol is used, the serial interface
retracts and asserts RTS in response to same conditions as for XON/XOFF protocol.
Note
Remote Commands and Syntax
Input Buffer Operation
6
6-3
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