Status Byte And Service Request (Srq) - Keithley 2302 Instruction Manual

8-6 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 8-3
Status byte and service request
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Figure 8-3
Service
* STB?
Request
Serial Poll
Generation
OR
* SRE
* SRE?
Decimal
Weights
shows the structure of these registers.
Status Summary Messages (6)
RQS
OSB ESB MAV QSB
(B6)
(B7) MSS (B5) (B4) (B3)
&
&
&
OSB ESB MAV QSB
(B7) (B6) (B5) (B4) (B3)
128 32 16
7 5 4
(2 ) (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
EAV Status Byte
MSB
(B1) (B0)
(B2) Register
&
&
&
EAV MSB
Service Request
(B1) (B0)
(B2)
Enable Register
8 4 1
3 2 0
) (2 ) (2 )