Anritsu MS8608A, Руководство по эксплуатации, Страница: 239 / 338

SECTION 4 STATUS STRUCTURE
4-7
Reading and clearing the STB register
The STB register can be read using serial polling or the
∗
STB?
common query. The
IEEE488.1 STB message can be read by either method, but the value sent to bit 6
(position) is different for each method.
The STB register contents can be cleared using the
∗
CLS command.
(1) Reading by serial polling (only when the GPIB interface bus is used)
The IEEE488.1 serial polling allows the device to return a 7-bit status byte and an RQS
message bit which conforms to IEEE488.1. The value of the status byte is not changed
by serial polling. The device sets the
RQS
message to 0 immediately after being polled.
(2) Reading by the
∗
STB? common query
The
∗
STB?
common query requires the devices to send the contents of the STB register
and the integer format response messages, including the MSS (Master Summary Status)
summary message. Therefore, except for bit 6, which represents the MSS summary
message, the response to
∗
STB? is identical to that of serial polling.
(3) Definition of MSS (Master Summary Message)
MSS indicates that there is at least one cause for a service request. The MSS message
is represented at bit 6 response to an
∗
STB? query, but it is not produced as a response
to serial polling. It should not be taken as part of the status byte specified by IEEE488.1.
MSS is configured by the overall logical OR in which the STB register and SRQ enable
(SRE) register are combined.
(4) Clearing the STB register using the
∗
CLS common command
The
∗
CLS common command clears all status data structures as well as the summary
messages corresponding to them.
The
∗
CLS command does not affect the settings in the Enable Register.