Eoi And Bus Hold-Off Modes (K) - Keithley 595 Instruction Manual

4.9.21 EOI and Bus Hold-off Modes (K)
Purpose
Provides control over whether or not the instrument sends the EOI stahls at the end
of its data string, and whether or not bus activity is held off (through the NRFD
line) until alI commands sent to the instrument are internally processed once the
instrument receives the X character.
Format Kn
Parameters
n = 0 Send EOI with last bytes-of reading; hold off bus until com-
mands processed on X.
n=l Do not send EOI with last byte of reading; hold off bus until commands
processed on X.
n=2 Send EOI with last byte of reading; do not hold off on X.
n=3 Do not send EOI with last byte of reading; do not hold off on X.
Description
The EOI line on the IEEE-488 bus provides a method to positively identify the last
byte in a multi-byte transfer sequence. Keep in mind that some controllers rely on
EOI to terminate their input sequences. In this case, suppressing EOI with the K
command may cause the controller input sequence to hang unless other terminator
sequences are used.
Bus hold off allows the instrument to temporarily hold up bus operation when its
receives the X character until it processes all commands sent in the command string.
The purpose ~of the hold off is to etikiY* that~ the front end FETs and relays are pro-
perly configured before taking a reading. Keep in mind that all bus operation will
cease for the hold off duration-not just activityassodated with the Model 595.~The
advantage of this is that no bus commands ~wilI be missed while the instrument is
processing commands previously received. Use the ready bit of the serial poll byte
(see paragraph 4.9.20) when not-holding off on X.
The hold off period depends on the commands being processed. Table 4-7 lists hold-
off times for a number of different commands.
Table 4-7. Bus Hold-Off Times
Command X Hold Off/Busy Until
J19
Permanent storage completed (l3msec)
F, R, Z
Model 595 front panel is set up (2Omsec)
&SE
Calculate calibration constant (5msec)
As soon as 'X" is recognized (met)
NOTE: RFD will be held off until each byte in is recognized (?.-6Omsec in continuous,
2mec is single shot); only exceeds 2msec for one character while reading is calculated.
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