IEEE-488 GPIB Interface
20
P
refixes
(Px)
Function
Turns the prefix mode on or off. Set x to:
“Y” to enable prefixes.
“N” to disable prefixes.
Remarks
Prefixes are sent over the bus with the measurement, and indicate the status of the current
measurement (see
Table
10
for examples):
“FC”,”FD”,”RC”,”RD”,”SW”,”RL”,”MN”,”MX” indicates the measurement type.
“U” indicates underflow; the value sent is “.000”.
“O” indicates overflow; the value sent is “199.9”.
“N” indicates normal; the value sent is a normal on-scale reading.
“4421” indicates the Bird model number.
Table 10
Prefix
Examples
T
riggers
(Tx)
Function
Selects the condition which will trigger a reading (see
Table
11
).
Remarks
Failure to trigger device before requesting a reading will lock the bus.
T1 halts the bus until a reading is available.
T0 and T1 do not set the measurement complete SRQ.
T2, T3, T4, and T5 set a SRQ when the measurement is complete.
Fastest reading rate is 2.4 readings/second; slowest is 1 reading/sec.
Table 11
Trigger
Conditions
Data String
Description
NFC.0.123W(CR)(LF)
Normal (N) forward carrier wave (FC), prefixes on
OFC 199.9W(CR)(LF)
Overflowed (O) forward carrier wave (FC), prefixes on
199.9W(CR)(LF)
Overflowed forward carrier wave, prefixes off
URD
.000W(CR)(LF)
Underflowed (U) reflected dBm (RD), prefixes on
Command
Trigger Condition
T0
Continuous on talk
T1
One shot on talk
T2
Continuous on GET
T3
One shot on GET
T4
Continuous on measurement command (FC,FD,
RC, RD, SW, RL, MN, MX)
T5
One shot on measurement command (FC, FD,
RC, RD, SW, RL, MN, MX)