Responding To A Parallel Poll - National Instruments Corporation GPIB-1014P User Manual

Section Five
second device might be assigned to respond with the remote message PPR3 (driving DIO3),
both positive (that is, true response if ist=1). Local configuration is static in that it does not
change after the system is integrated (that is, hardware configured and installed).
• Remote configuration (Parallel Poll function subset PP1) involves the dynamic assigning of the
response line and sense to devices on the GPIB. This is accomplished using Parallel Poll
Enable (PPE) and Parallel Poll Disable (PPD) commands, which are issued by the Active
Controller. The sequence for remotely configuring devices on the GPIB is as follows:
1. Become Active Controller.
2. Send the GPIB UNL message to unaddress all GPIB Listeners.
3. Send the listen address of the first device to be configured.
4. Send the GPIB PPC message to all devices followed by the PPE message for that device.
5. Repeat from the second step (UNL) for each additional device.
The same procedure should be followed to disable polling with PPD (for example, when changing
responses during reconfiguration).

Responding To a Parallel Poll

Before the GPIB-1014P can be polled by the CIC, the TLC must be configured either locally by
your program at initialization time or remotely by the CIC. Configuration involves the following:
• Enabling the TLC to participate in polls
• Selecting the sense or polarity of the response
• Selecting the GPIB data line on which the response will be asserted when the CIC issues the
IDY message
With remote configuration (PP1), the TLC interprets the configuration commands received from the
CIC, without any software assistance or interpretation from your program. With local configuration
(PP2), the three actions listed must be explicitly handled in the software by writing the appropriate
values to the U, S, and P3 to P1 bits of the PPR. Refer to the PPR description in Section Four for
more information.
Once the PPR is configured, all that remains for your program is determining the source and value
of the local individual status (ist) message. If the ISS bit in the AUXRB is zero, ist is set and
cleared via the Set and Clear Parallel Poll auxiliary commands. If ISS is one, ist is set if the TLC's
Service Request function is in the Service Request State (SRQS) and the TLC is asserting the GPIB
SRQ signal line and cleared otherwise. Consequently, setting ISS ties the Parallel Poll function to
the Service Request function and also to the Serial Poll process.
The particular response sent by the GPIB-1014P during a Parallel Poll is determined by the value of
ist and the configuration of the GPIB-1014P. The value of ist and the actual configuration must be
decided by the GPIB system integrator. The response can be changed dynamically during program
execution by changing the value of ist and, when remote configuration is used, by reconfiguration.
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Programming Considerations
GPIB-1014P User Manual