Lakeshore 336, Руководство пользователя

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6.2.6 Status System Detail: Status Byte Register and Service Request 103
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6.2.6.4 Using Status Byte Query (*STB?)
The Status Byte Query (*STB?) command is similar to a serial poll except it is pro-
cessed like any other instrument command. The *STB? command returns the same
result as a serial poll except that the Status Byte bit 6 (RQS/MSS) is not cleared. In this
case, bit 6 is considered the MSS bit. Using the *STB? command does not clear any bits
in the Status Byte Register.
6.2.6.5 Using the Message Available (MAV) Bit
Status Byte summary bit 4 (MAV) indicates that data is available to read into the bus
controller. This message may be used to synchronize information exchange with the
bus controller. The bus controller can, for example, send a query command to the
Model 336 and then wait for MAV to set. If the MAV bit has been enabled to initiate an
SRQ, the user’s program can direct the bus controller to look for the SRQ leaving the
bus available for other use. The MAV bit will be clear whenever the output buffer is
empty.
6.2.6.6 Using Operation Complete (*OPC) and Operation Complete Query (*OPC?)
The Operation Complete (*OPC) and Operation Complete Query (*OPC?) are both
used to indicate when pending device operations complete. However, the commands
operate with two distinct methods.
The *OPC command is used in conjunction with bit 0 (OPC) of the Standard Event Sta-
tus Register. If *OPC is sent as the last command in a command sequence, bit 0 will be
set when the instrument completes the operation that was initiated by the command
sequence. Additional commands may be sent between the instrument and the bus
controller while waiting for the initial pending operation to complete. A typical use of
this function would be to enable the OPC bit to generate an SRQ and include the *OPC
command when programming the instrument. The bus controller could then be
instructed to look for an SRQ allowing additional communication with the instru-
ment while the initial process executes.
The *OPC? query has no interaction with bit 0 (OPC) of the Standard Event Status Reg-
ister. If the *OPC? query is sent at the end of a command sequence, the bus will be
held until the instrument completes the operation that was initiated by the com-
mand sequence. Additional commands (except *RST) should not be sent until the
operation is complete, as erratic operation will occur. Once the sequence is complete
a 1 will be placed in the output buffer. This function is typically used to signal a com-
pleted operation without monitoring the SRQ. It is also used when it is important to
prevent any additional communication on the bus during a pending operation.
Command or Operation Description
*ESR? Read and clear the Standard Event Status Register
*ESE 32 Enable the Command Error (CME) bit in the Standard Event Status Register
*SRE 32 Enable the Event Summary Bit (ESB) to set the RQS
*ABC Send improper command to instrument to generate a command error
Monitor bus Monitor the bus until the Service Request interrupt (SRQ) is sent.
Initiate serial poll Serial poll the bus to determine which instrument sent the interrupt
and clear the RQS bit in the Status Byte.
*ESR? Read and clear the Standard Event Status Register allowing
an SRQ to be generated on another command error.
TABLE 6-4 Programming example to generate an SRQ