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Programming the Attenuator
How the Attenuator Receives and Transmits Messages
b. Clears Bit 7 (MSB).
2. No modification is made inside strings or binary blocks. Outside
strings and binary blocks, the following modifications are made:
a. Lower-case characters are converted to upper-case.
b. The characters 00
16
to 09
16
and 0B
16
to 1F
16
are converted
to spaces (20
16
).
c. Two or more blanks are truncated to one.
3. An EOI (End Or Identify) sent with any character is put into the
input queue as the character followed by a line feed (LF, 0A
16
).
If EOI is sent with a LF, only one LF is put into the input queue.
4. The parser starts if the LF character is received or if the input
queue is full.
Clearing the Input Queue
Switching the power off, or sending a Device Interface Clear signal,
causes commands that are in the input queue, but have not been
executed to be lost.
The Output Queue
The output queue contains responses to query messages. The
attenuator transmits any data from the output queue when a
controller addresses the instrument as a talker.
Each response message ends with a LF (0A
16
), with EOI=TRUE. If
no query is received, or if the query has an error, the output queue
remains empty.
The Message Available bit (MAV, bit 4) is set in the Status Byte
register whenever there is data in the output queue.
The Error Queue
The error queue is 30 errors long. It is a FIFO queue (first-in first-
out). That is, the first error read is the oldest error to have occurred.
A new error is only put into the queue if it is not already in it.