Stanford Research Systems SR780, Operating Manual And Programming Reference

Page: 473 / 497

Status Word Definitions 5-107
SR780 Network Signal Analyzer
Status Word Definitions
The SR780 reports on its status by means of six status words: the Serial Poll,
Standard Event, Instrument, Display, Input and Error status words.
Upon power-on, the SR780 may either clear all of its status enable registers or
maintain them in the state they were in on power-down. The *PSC command
determines which action will be taken.
The status bits are set to 1 when the event or state described in the tables below
has occurred or is present.
Serial Poll Status Word
Bit Name Set when
0 INST An enabled bit in the Instrument status word is set
1 DISP An enabled bit in the Display status word is set
2 INPT An enabled bit in the Input status word is set
3 IERR An enabled bit in the Error status word is set
4 MAV The interface output buffer is not empty
5 ESB An enabled bit in the Standard status word is set
6 SRQ An SRQ has occurred (serial poll), or
an enabled bit in the this status word is set (*STB?)
7 IFC No command execution is in progress
The INST, DISP, INPT, IERR and ESB bits are set whenever any bit in both
their respective status words AND enable registers is set. Use the INSE, DSPE,
INPE, ERRE and *ESE commands to set the enable register bits. The INST,
DISP, INPT, IERR and ESB status bits are not cleared until ALL enabled status
bits in the Instrument, Display, Input, Error and Standard Event status words are
cleared (by reading the status words or using *CLS).
Use serial poll or *STB? to read the Serial Poll status. Use *SRE to set bits in the
Serial Poll enable register.
Using *STB? to Read the Serial Poll Status
The Serial Poll status word is NOT cleared by reading the status using *STB?. A
bit stays set as long as the status condition exists. This is true even for bit 6
(SRQ). Bit 6 will be set whenever the same bit in the Serial Poll status word
AND Serial Poll enable register is set. This is independent of whether a serial
poll has occurred to clear the service request.
Using Serial Poll to Read the Serial Poll Status
Except for SRQ, a bit in the Serial Poll status word is NOT cleared by serial
polling the status word. A bit stays set as long as the status condition exists.
When reading the status using a serial poll, the SRQ bit signals that the SR780 is
requesting service. The SRQ bit will be set (1) the first time the SR780 is polled
following a service request. The serial poll automatically clears the service