Lake Shore 335, Руководство пользователя

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98 c
HAPTER
6: Computer Interface Operation
Model 335 Temperature Controller
D
Event Summary (ESB), Bit (5): this bit is set when an enabled standard event has
occurred
D
Message Available (MAV), Bit (4): this bit is set when a message is available in the
output buffer
6.2.6.2 Service Request Enable Register
The Service Request Enable Register is programmed by the user and determines
which summary bits of the Status Byte may set bit 6 (RQS/MSS) to generate a Service
Request. Enable bits are logically ANDed with the corresponding summary bits

(FIGURE 6-4). Whenever a summary bit is set by an event register and its correspond-
ing enable bit is set by the user, bit 6 will set to generate a service request. The Service
Request Enable command (*SRE) programs the Service Request Enable Register and
the query command (*SRE?) reads it.
Status byte register and service request enable register
RQS
MSS
Generate service
request—reset by
serial poll
Read by *STB?
7 6 5 4 3 2 1 0
AND
OR
AND
AND
7 6 5 4 3 2 1 0
OSB MSS ESB RQS MAV
Not
used
Not
used
Not
used
Not
used
OSB ESB Not used MAV
Not
used
Not
used
Not
used
Not
used
– Decimal
– Name
– Bit
– Bit
– Name
Status byte register
*STB?
Service request
enable register
*SRE, *SRE?
From operation event register
From standard event status register
From operation event register
8 4 2 1 16 32 64 128
8 4 2 1 16 32 64 128
6.2.6.3 Using Service Request (SRQ) and Serial Poll
When a Status Byte summary bit (or MAV bit) is enabled by the Service Request
Enable Register and goes from 0 to 1, bit 6 (RQS/MSS) of the status byte will be set.
This will send a service request (SRQ) interrupt message to the bus controller. The
user program may then direct the bus controller to serial poll the instruments on the
bus to identify which one requested service (the one with bit 6 set in its status byte).
Serial polling will automatically clear RQS of the Status Byte Register. This allows sub-
sequent serial polls to monitor bit 6 for an SRQ occurrence generated by other event
types. After a serial poll, the same event or any event that uses the same Status Byte
summary bit, will not cause another SRQ unless the event register that caused the
first SRQ has been cleared, typically by a query of the event register.
The serial poll does not clear MSS. The MSS bit stays set until all enabled Status Byte
summary bits are cleared, typically by a query of the associated event register

(section 6.2.6.4).
The programming example in TABLE 6-4 initiates an SRQ when a command error is
detected by the instrument.
FIGURE 6-4