2606B System SourceMeter® Instrument Reference Manual
Appendix E: Status model
2606B-901-01 Rev. B / May 2018
E-15
Service Request Enable Register
The Service Request Enable Register controls the generation of a service request. This register is
programmed by the user and is used to enable or disable the setting of bit B6 (RQS/MSS) by the
Status Summary Message bits (B0, B1, B2, B3, B4, B5, and B7) of the Status Byte Register. As
shown in the Status Byte Register topic, a logical AND
operation is performed on the summary bits
(&) with the corresponding enable bits of the Service Request Enable Register. When a logical AND
operation is performed with a set summary bit (1) and with an enabled bit (1) of the enable register,
the logic “1” output is applied to the input of the logical OR gate and, therefore, sets the MSS/RQS bit
in the Status Byte Register.
The individual bits of the Service Request Enable Register can be set or cleared by using the
*SRE
common command or
status.request_enable
. To read the Service Request Enable Register,
use the
*SRE?
query or
print(status.request_enable)
. The Service Request Enable Register
clears when power is cycled or a parameter value of 0 is sent with a status request enable command
(for example, a
*SRE 0
or
status.request_enable = 0
is sent). The commands to program and
read the SRQ Enable Register are listed in
Status byte and service request commands
(on page E-
Serial polling and SRQ
Any enabled event summary bit that goes from 0 to 1 sets bit B6 and generates a service request
(SRQ).
In your test program, you can periodically read the Status Byte to check if an SRQ has occurred and
what caused it. If an SRQ occurs, the program can, for example, branch to an appropriate subroutine
that will service the request.
SRQs can be managed by the serial poll sequence of the instrument. If an SRQ does not occur, bit
B6 (RQS) of the Status Byte Register remains cleared, and the program proceeds normally after the
serial poll is performed. If an SRQ does occur, bit B6 of the Status Byte Register is set, and the
program can branch to a service subroutine when the SRQ is detected by the serial poll.
The serial poll automatically resets RQS of the Status Byte Register. This allows subsequent serial
polls to monitor bit B6 for an SRQ occurrence that is generated by other event types.
The serial poll does not clear the low-level registers that caused the SRQ to occur. You must clear
the low-level registers explicitly. Refer to
(on page E-11).
For common commands and TSP commands, B6 is the MSS (Message Summary Status) bit. The
serial poll does not clear the MSS bit. The MSS bit remains set until all enabled Status Byte Register
summary bits are reset.
Status byte and service request commands
The commands to program and read the Status Byte Register and Service Request Enable Register
are listed in the table below. Note that the table includes both common commands and their script
command equivalents. For details on programming and reading registers, see
(on page E-12) and
(on page E-12).
To reset the bits of the Service Request Enable Register to 0, use 0 as the parameter value for the
command (for example,
*SRE
0
or
status.request_enable = 0
).
