Keysight E4980A User Manual page 267

Overview of Remote Control
Status Byte
Table 8-1
weights. When you read the status byte using GPIB serial polling, the value is
the sum of the total bit weights of all the high bits existing at the time you read
the byte. After serial polling of the status byte, only bit 6 (RQS) is cleared.
Table 8-1 Status Bit definition of the Status Byte Register
Bit No. Bit Name
Weight
0 1 unused
1 2 unused
2 4 unused
3 8 unused
4 16 MAV (message available)
5 32 Standard Event Status Register
Summary
6 64 RQS
7 128 Operation Status Register
Summary
Keysight E4980A/AL Precision LCR Meter
gives the individual bit assignments of the status byte and its bit
Description
always 0 (zero)
always 0 (zero)
always 0 (zero)
always 0 (zero)
This bit is set to "1" when the E4980A/AL has available data to output
that have not been read yet. This bit is reset to "0" when all the data
have been retrieved. (This bit is not cleared by serial polling.)
This bit is set to "1" when any enabled bits of the standard event status
register have been set to "1." This bit is cleared when all bits of the
standard event status register are set to "0." (This bit is not cleared by
serial polling).
Bit 6 serves two functions (RQS/MSS), depending on how it is read.
RQS (Request Service) Bit
If bit 6 is read in the serial polling process, it is treated as an RQS bit
and is reset during the serial polling process.

MSS (Master Summary) Bit
If bit 6 is read using the *STB? (status byte) query, it is treated as an
MSS bit, and its value is not changed by executing the *STB? query.

To understand this operation, think of the RQS and MSS bits as two
inputs to a multiplexer (MUX) and the output of the MUX being bit 6 of
the status byte register.

During the serial polling operation the MUX path selected is from the
service request generation circuit to bit 6, so bit 6 represents the RQS
bit.

During execution of the *STB? query the MUX path selected is from
the master summary bit generation circuit to bit 6, so bit 6 represents
the MSS bit.

To clear the MSS bit, all bits of the original registers corresponding to
the enabled summary bit in the status byte and the output buffer of the
E4980A/AL must be cleared. When you read the status byte including
the MSS bit instead of the RQS bit, the *STB? query must be used. The
*STB? query clears neither the MSS bit nor the RQS bit.
This bit is set to "1" when one or more enabled bits of the operation
status register is set to "1." This bit is cleared when all bits of the
operation status register are set to 0. (This bit is not cleared by serial
polling.)
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