G P I B / I E E E 4 8 8 . 2 R E M O T E O P E R A T I O N
Input Buffer and Output Data
01_10
OMM-6810B
45
C H A P T E R
3
prematurely. However, in most cases, the individual operation will be completed
immediately.
The speed of writing to non-volatile memory (NVRAM) is slow compared to
processor speed, and the new information (to be written) is placed on a queue to
reduce the processor overhead for non-volatile storage operations. However, the
new information (i.e. new parameter value) is buffered and is essentially stored as
soon as the command which created it is parsed. Therefore, even though the
OPC flag may not be set immediately after a new parameter value is created, the
new value is stored for all intents and purposes, and command throughput is not
directly related to the OPC rate.
Whenever there is response data in the Output Queue, bit 4 is set in the Status
Byte Register. Whenever there is any error message in the Error Queue, bit 7 is
set in the Status Byte Register.
Input Buffer and Output Data
The Input buffer is 80 bytes long. The <PROGRAM MESSAGE> may be longer,
however.
The output (response) data of the 6810B is sent in blocks of up to 80 bytes in
length. It is sent using high speed DMA within the 6810B, but may be of indefinite
length. Although some commands have a definite length response, such as the
"MESsage?" query, the response length is indefinite because the 6810B responds
to multiple queries in a single response output. The user may enter as many
queries as desired in a single input message, and the 6810B responds to all of
them in the same output message, if possible.
All query responses are evaluated at the time the query is parsed, and not at the
time the response message is sent. In most cases this does not create a problem
since the time between parsing a query and sending its response is small, unless
the GPIB controller takes a long time to request the response.
Remote Interface Messages
The following sections are intended as a reference for using the 6810B with the
GPIB option when an understanding of the lower level interface messages is
required. These sections deal with the remote interface messages which are
available with the instrument, and they contain a list of the Interface Function
subsets. This information is generally not required by the user unless there is a
question of compatibility of the instrument with a specific controller. A list of
