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Model 2790 SourceMeter
Status byte register
The summary messages from the status registers and queues are used to set or clear the
appropriate bits (B0, B2, B3, B4, B5, and B7) of the Status Byte Register. These summary
bits do not latch and their states (0 or 1) are solely dependent on the summary messages (0 or
1). For example, if the Standard Event Register is read, its register will clear. As a result, its
summary message will reset to 0, which in turn will reset the ESB bit in the Status Byte Reg-
ister.
The bits of the Status Byte Register are described as follows:
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Depending on how it is used, Bit B6 of the Status Byte Register is either the Request for
Service (RQS) bit or the Master Summary Status (MSS) bit:
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Bit B0, Measurement Summary Bit (MSB) — Set summary bit indicates that an
enabled measurement event has occurred.
Bit B1 — Not used.
Bit B2, Error Available (EAV) — Set summary bit indicates that an error or status
message is present in the Error Queue.
Bit B3, Questionable Summary Bit (QSB) — Set summary bit indicates that an
enabled questionable event has occurred.
Bit B4, Message Available (MAV) — Set summary bit indicates that a response
message is present in the Output Queue.
Bit B5, Event Summary Bit (ESB) — Set summary bit indicates that an enabled
standard event has occurred.
Bit B6, Request for Service (RQS)/Master Summary Status (MSS) — Set bit
indicates that an enabled summary bit of the Status Byte Register is set.
Bit B7, Operation Summary Bit (OSB) — Set summary bit indicates that an
enabled operation event has occurred.
When using the serial poll sequence of the Model 2790 to obtain the status byte
(a.k.a. serial poll byte), B6 is the RQS bit. See
page
11-8, for details on using the serial poll sequence.
When using the *STB? command
MSS bit.
"Serial polling and SRQ,"
(Table
11-2) to read the status byte, B6 is the
11-7
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