Fluke DDS Function Generator 271, User Manual

Page: 97 / 132

Remote Operation
Remote Operation
16
16-7
The IEEE 488.2
DEADLOCK
error is handled as follows. If the response formatter is
waiting to send a response message and the input queue becomes full then the instrument
enters the
DEADLOCK
state and an error is generated. This will cause the Query Error
bit to be set in the Standard Event Status Register, a value of 2 to be placed in the Query
Error Register and the response formatter to be reset thus clearing the output queue. The
parser will then start parsing the next
<PROGRAM MESSAGE UNIT>
from the input
queue. See Status Reporting below for further information.
GPIB Parallel Poll
Complete parallel poll capabilities are provided in this instrument. The Parallel Poll
Enable Register is set to specify which bits in the Status Byte Register are to be used to
form the
ist
local message The Parallel Poll Enable Register is set by the
*PRE
<nrf>
command and read by the
*PRE?
command. The value in the Parallel Poll
Enable Register is ANDed with the Status Byte Register; if the result is zero then the
value of
ist
is 0, otherwise the value of
ist
is 1.
The instrument must also be configured so that the value of
ist
can be returned to the
controller during a parallel poll operation. The instrument is configured by the controller
sending a Parallel Poll Configure command (
PPC
) followed by a Parallel Poll Enable
command (
PPE
). The bits in the
PPE
command are shown below:
bit 7 = x don't care
bit 6 = 1
bit 5 = 1
bit 4 = 0
parallel poll enable
bit 3 = sense sense of the response bit; 0 = low, 1 = high
bit 2 = ?
bit 1 = ?
bit 0 = ?
bit position of the response
Example: to return the
RQS
bit (bit 6 of the Status Byte Register) as a 1 when true and a
0 when false in bit position 1 in response to a parallel poll operation send the following
commands:
*PRE 64<pmt>
, then
PPC
followed by
69H
(
PPE
)
The parallel poll response from the generator will then be
00H
if
RQS
is 0 and
01H
if
RQS
is 1.
During parallel poll response the DIO interface lines are resistively terminated (passive
termination). This allows multiple devices to share the same response bit position in
either wired AND or wired OR configuration. Refer to the IEEE 488.1 specification for
more information.
Status Reporting
This section describes the complete status model of the instrument. Note that some
registers are specific to the GPIB section of the instrument and are of limited use in an
RS232 environment.
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