Cannot access Port C (8255) line 0,1,2, Port A=mode 2, Port B=mode 0.

[simk]

DIO-24 with 8255 chip. Port A is mode 2 (bi-dir). Port B is mode 0 (output only). With this, Port C left line 0,1,2. Manage to cofigure these line either output or input but cannot access to it.

Have try prt/line function but with errors.

How can these three line be access by NI lib?

[AlanArmstead]

It would help if you could provide a little more information. Are you able to use test panels with Port C in Measurement & Automation Explorer? What development environment are you using? What function are you using to try to write/read from the lines?

-Alan A.

[Salvador_Santolucito]

Hi Simk,

When using Bi-directionl mode with the 8255 chip, some of the lines on Port C are reserved for handshaking. This is why you are having trouble accessing. For more information on this check out the following KnowledgeBase:

http://digital.ni.com/public.nsf/websearch/F865C1157622C9DE8625648B00782CDA?OpenDocument

-Sal