Status Byte And Service Request (Srq) - Keithley 2303 User Manual

7-6 Status Structure

Status byte and service request (SRQ)

Service request is controlled by two 8-bit registers; the status byte register and the service
request enable register. Figure 7-3 shows the structure of these registers.
Figure 7-3
Status byte and service request
Service
Request
Generation
Status Summary Messages (6)
RQS
OSB ESB MAV
(B6)
* STB?
Serial Poll (B7) MSS (B5) (B4)
&
&
OR
* SRE
OSB ESB MAV
(B7) (B6) (B5) (B4)
* SRE?
128 32
Decimal
Weights 7 5
(2 ) (2 ) (2
OSB = Operation Summary Bit
MSS = Master Summary Status
RQS = Request for Service
ESB = Event Summary Bit
MAV = Message Available
QSB = Questionable Summary Bit
EAV = Error Available
MSB = Measurement Summary Bit
& = Logical AND
OR = Logical OR
QSB EAV Status Byte
MSB
(B1) (B0)
(B3) (B2) Register
&
&
&
&
QSB EAV MSB
Service Request
(B1) (B0)
(B3) (B2)
Enable Register
16 8 4 1
4 3 2 0
) (2 ) (2 ) (2 )