BIRD THRULINE 4020 series, Инструкция, Страница: 31 / 74

IEEE-488 GPIB Interface
19
Serial Polling Enable/Disable (SPE/SPD)
Function
Enables or disables the serial polling sequence.
Remarks
The SPE command puts all devices in serial poll mode waiting to be
addressed. The SPD command clears the SRQ bit (bit 6) and ends the polling
sequence.
When addressed a device sends its status byte to the controller. A value of 1
for a bit means that the device condition that bit refers to is true. A value of 0
means that the condition is false.
The 4421 does not use all bits of the statu s byt e. F igu r e 15 list s t h e bit s u sed,
along with a description and how to reset them.
CAUTION
During remote operation, periodically monitor the bus service request line.
Failure to detect a service request could result in equipment damage.
Figure 15
IEEE Status
Byte Description
Bit Name Condition
6 SRQ
Set if a ser vice r equ est is gen er a t ed by t h e
4421. If a n SRQ h a s been r eceived by t h e
con t r oller a n d t h is bit is clea r ed, ot h er
in st r u m en t s on t h e bu s sh ou ld be ch eck ed t o
det er m in e wh er e t h e SRQ occu r r ed.
Clea r ed by a ser ia l poll of t h e 4421.
3 Measurement
Complete
Set wh en t h e power m et er h a s com plet ed a
reading.
Clea r ed by r equ est in g a r ea din g over t h e bu s.
2 Reading
Underflow
Set wh en t h e RF power is u n der r a n ge a n d a
r ea din g h a s been com plet ed.
Clea r ed by r equ est in g a r ea din g over t h e bu s.
1 Reading Overflow Set wh en t h e RF power is over r a n ge a n d a
r ea din g h a s been com plet ed.
Clea r ed by r equ est in g a r ea din g over t h e bu s.
0 Error
Set if a n illega l device-depen den t com m a n d
(IDDC) or illega l device-depen den t com m a n d
opt ion (IDDCO) wa s r eceived, or if t h e power
m et er fa ils t h e self t est .
Cleared by reading the U1 status word. The U1
on pa ge 25.