Going From Active To Idle Controller; The Gpib-1014P As Gpib Talker And Listener; Programmed Implementation Of Talker And Listener; Addressed Implementation Of The Talker And Listener - National Instruments Corporation GPIB-1014P User Manual

Section Five

Going from Active to Idle Controller

Going from Active to Idle GPIB Controller, also known as passing control, requires that the TLC
be the Active Controller initially (in order to send the necessary GPIB command messages). After
the TLC has become the GPIB Active Controller, it must complete the following procedures to pass
control:
1. Write the GPIB Talk address of the device being passed control to the CDOR.
2. In response to the next CO status, write the GPIB TCT message to the CDOR.
3. As soon as the TCT command message is accepted by all devices on the GPIB, the TLC
automatically unasserts ATN and the new Controller asserts ATN.

The GPIB-1014P as GPIB Talker and Listener

The TLC can be either GPIB Talker or Listener, but not both simultaneously. Either function is
deactivated automatically if the other is activated. The TA, LA, and ATN* bits in the ADSR
together indicate the specific state of the TLC:
ATN*
0 1
The status bits Address Status Change (ADSC), Command Output (CO), Address Pass Through
(APT), Data Out (DO), and Data In (DI) are used to prompt the program (possibly with an
interrupt request) when a change of state occurs.
The following paragraphs discuss several aspects of data transfers.

Programmed Implementation of Talker and Listener

When there is no Controller in the GPIB system, the ton and lon address modes (refer to the
description of the ADMR) are used to activate the TLC GPIB Talker and Listener functions. If
used, ton or lon should be set during TLC initialization.
When the TLC is GPIB Active Controller, the Listen and Local Unlisten programmed auxiliary
commands are used to activate and de-activate the TLC GPIB Listener function.

Addressed Implementation of the Talker and Listener

The TLC, when GPIB Active Controller, can address itself by sending its own GPIB Talk or Listen
address using the CO bit and the CDOR. When another device on the GPIB is acting as Controller,
the TLC is addressed with GPIB command messages to become a Talker or Listener.
© National Instruments Corporation
TA LA
0 Addressed Talker–cannot send data
1 1 0
0 0 1
1 0 1
Active Talker–can send data
Addressed Listener–cannot receive data
Active Listener–can receive data
5-5
Programming Considerations
GPIB-1014P User Manual