ICS ELECTRONICS 9099, Instruction Manual

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A-7
A1
A1.2.3 IEEE 488.2 Common Commands
The IEEE 488.2 Standard also mandated a list of required and optional Com-
mon Commands that all 488.2 devices could support. All of the 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-1 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 pend-
ing 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.