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three wire handshaking process
Polson
Member
07-10-2001 03:43 PM
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Thanks in advance for any help.
I am using the TNT4882 Asic, which is being controlled by a microcontroller. I have several questions:
1. Should the TNT automatically respond to commands sent to it over the GPIB bus and how should it respond. (Ibwrt, Ibrd...etc)
2. If so, should the TNT, on its own, respond with the proper three wire handshaking signals, or must I manually control those signals with my microcontroller
Currently, when I attach my instrument to a GPIB CIC and attempt to establish communication for the first time, the CIC sends the hex value 41 to my instrument, which is the command to make the device at address 1 a talker. The ATN line asserts, the nrfd line asserts then quickly unasserts and
stays in that state forever and the ndac line asserts stays in that state indefinitely. The DAV line does nothing, which surprised me since the CIC should be in control of that signal when sending a command. After this point, no changes occur on the GPIB lines. At this point do I have to manually unassert the NDAC line and reassert the NRFD line to complete the gpib command transaction as per figure C-5 in the TNT manuel? Or what else must I do such that the commands sent by the CIC are recognized by the TNT? If you have any assembly or even C code which would show me how the TNT should respond during the three wire handshaking process, I would appreciate it.
I am using the TNT4882 Asic, which is being controlled by a microcontroller. I have several questions:
1. Should the TNT automatically respond to commands sent to it over the GPIB bus and how should it respond. (Ibwrt, Ibrd...etc)
2. If so, should the TNT, on its own, respond with the proper three wire handshaking signals, or must I manually control those signals with my microcontroller
Currently, when I attach my instrument to a GPIB CIC and attempt to establish communication for the first time, the CIC sends the hex value 41 to my instrument, which is the command to make the device at address 1 a talker. The ATN line asserts, the nrfd line asserts then quickly unasserts and
stays in that state forever and the ndac line asserts stays in that state indefinitely. The DAV line does nothing, which surprised me since the CIC should be in control of that signal when sending a command. After this point, no changes occur on the GPIB lines. At this point do I have to manually unassert the NDAC line and reassert the NRFD line to complete the gpib command transaction as per figure C-5 in the TNT manuel? Or what else must I do such that the commands sent by the CIC are recognized by the TNT? If you have any assembly or even C code which would show me how the TNT should respond during the three wire handshaking process, I would appreciate it.
Kim L
Member
07-12-2001 12:27 PM
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The response of the chip is to assert the LA or TA bit. For a description of how the TNT responds to commands, go to page 4-7 of the TNT4882 Programmer Reference Manual. You'll find the link below.
http://digital.ni.com/manuals.nsf/caba5d53e9b015a186256793004eebb7/91aaba0122b5f7168625665e00691c89?OpenDocument
You do not have to do anything manually to control the handshaking. It is part of the 488 protocol and therefore, handled by the chip.
National Instruments provides a a source code package (ESP-488) that allows you to program the TNT4882 chip with ease. That might help you resolve the other issues that you are seeing. You can find the ESP-488 by following the link below.
http://digital.ni.com/softlib.nsf/current?OpenView&Start=1&Count=500&Expand=6#6
Kim
L.
Applications Engineer
National Instruments
http://digital.ni.com/manuals.nsf/caba5d53e9b015a186256793004eebb7/91aaba0122b5f7168625665e00691c89?OpenDocument
You do not have to do anything manually to control the handshaking. It is part of the 488 protocol and therefore, handled by the chip.
National Instruments provides a a source code package (ESP-488) that allows you to program the TNT4882 chip with ease. That might help you resolve the other issues that you are seeing. You can find the ESP-488 by following the link below.
http://digital.ni.com/softlib.nsf/current?OpenView&Start=1&Count=500&Expand=6#6
Kim
L.
Applications Engineer
National Instruments
