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525A
Users Manual
Programming the ESR and ESE
To read the contents of the ESR, send the remote command, *ESR?. The ESR is
cleared (set to 0) every time it is read. To read the contents of the ESE, send the
remote command, *ESE?. The ESE is not cleared when it is read. When you read
either register, the Calibrator responds by sending a decimal number that when
converted to binary represents bits 0 through 15.
Output Queue
The output queue is loaded whenever a query is processed, and holds up to 250
characters. The controller reads it with a statement such as a BASIC INPUT
statement, removing what it reads from the queue. If the queue is empty, the
Calibrator does not respond to the INPUT statement from the controller. The
Message Available (MAV) bit in the Serial Poll Status Byte is 1 if there is
something in the output queue and 0 if the output queue is empty.
Error Queue
When a command error, execution error, or device-dependent error occurs, its
error code is placed in the error queue where it can be read by the ERR? command.
(See Chapter 5 for a list of error messages.) Reading the first error with the ERR?
command removes that error from the queue. A response of 0 means the error
queue is empty. The error queue is cleared when you turn off the power, and when
you use the *CLS (Clear Status) common command.
The error queue contains up to 15 entries. If more than 15 errors occur, only the
first 15 errors are kept in the queue. A 16th entry in the queue is always an "error
queue overflow" error, and all later errors are discarded until the queue is at least
partially read. The first errors are kept, because if many errors occur before the
user can acknowledge and read them, the earliest errors are the most likely to point
to the problem. The later errors are usually repetitions or consequences of the
original problem.
Input Buffer Operation
As the Calibrator receives each data byte from the controller, it places the bytes in
a portion of memory called the input buffer. The input buffer holds up to 250 data
bytes and operates in a first in, first out fashion.
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