A-10
A
Common Commands start with an asterisk. Commands that end with a
question mark are queries. Query responses can be an ASCII number or an
ASCII string. Other numerical formats are legal as long as the device
supports the required ASCII format. Table A-2 lists the IEEE 488.2
Common Commands.
A1.2.4 IEEE 488.2 Differences From IEEE 488.1
The user who is familiar with the older 488.1 devices should take the
following differences into account when programming a 488.2 device.
A 488.2 device outputs the Status Byte Register contents plus the RQS bit
in response to a serial poll. The RQS bit is reset by the serial poll. The same
488.2 device outputs the Status Byte Register contents plus the MSS bit in
response to a *STB? query. The MSS bit is cleared when the condition is
cleared.
488.2 restricts the Device Clear to only clearing the device's buffers and
pending operations. It does not clear the Status Reporting Structure or the
output lines. Use *CLS to clear the Status Structure and *RST or *RCL to
reset the outputs.
488.2 commands are really special data messages and are executed by the
device's parser. Always allow sufficient time for the parser to execute the
commands before sending the device a 488.1 command. i.e. a Device Clear
sent too soon will erase any pending commands and reset the parser.
Enable Register values are only saved and restored if the *PSC command
is 0. A *PSC command of 1 causes zeros to be loaded into the enable
registers when the unit is next reset or powered on.
