Programming the Polarization Controller
GPIB Interface
44
Agilent
8169A
Polarization Controller, Second Edition
How the Polarization Controller Receives
and Transmits Messages
The polarization controller exchanges messages using an input and an
output queue. Error messages are kept in a separate error queue.
How the Input Queue Works
The input queue is a FIFO queue (first-in first-out). Incoming bytes are
stored in the input queue as follows:
1
Receiving a byte:
a
Clears the output queue.
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 0016 to 0916 and 0B16 to 1F16 are converted to spaces
(2016).
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, 0A16). 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.