Status Displays and Error Messages
Adjacent to the right alphanumeric displays, the Model Z9216 has three front panel status LEDs that
provide positive indication of commands and communications to help verify operations during the
development of control programs. The ACT LED flashes whenever a character is received or sent
over either interface. The ERR LED flashes when an error has been detected, such as an illegal
command, or parameter out of range. The REM LED is lit whenever the Model Z9216 is in a remote
state (front panel locked out).
The Model Z9216 reports two types of errors that may occur during command execution: command
errors and execution errors. Command errors are errors in the command syntax. For example,
unrecognized commands, illegal queries, lack of terminators, and non-numeric arguments are
examples of command errors. Execution errors are errors that occur during the execution of
syntactically correct commands. For example, out of range parameters and commands that are
illegal for a particular mode of operation are classified as execution errors.
The NO COMMAND bit is a bit in the serial poll register that indicates that there no commands waiting
to be executed in the input queue. This bit is reset when a complete command is received in the input
queue and is set when all of the commands in the queue have been executed. This bit is useful in
determining when all of the commands sent to the Model Z9216 have been executed. This is
convenient because some commands, such as taking a measurement, or auto calibration, take a long
time to execute and there ia no other way of determining when they are done. The NO COMMAND
bit may be read while commands are being executed by doing a GPIB serial poll. There is no way to
read this bit over RS232. Note that using the *STB? query to read this bit will always return the value
0 because it will always return an answer while a command is executing - the *STB? command itself.
Definitions of Status Bytes
Serial Polling
Bit Name Usage
0 Ready The Model Z9216 is ready to perform a measurement
1 Not used
2 Not used
3 LCR An unmasked bit in the LCR status register has been set.
4 MAV The GPIB output queue is non-empty
5 ESB An unmasked bit in the standard status byte has been set.
6 RQS / MSS SRQ (Service Request) bit.
7 No command There are no unexecuted commands in the input queue.
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