Register-Level Programming
6-7
Register-Level Programming
Note:
Ignore this section if you are using the Function Call Driver from
your ASO-PIO software package.
If your application goes beyond the capabilities of the software included
with your board, you must develop your own programming for control of
I/O functions. You can program the I/O functions because each group of
24 digital I/O channels on your PIO-SSR Series board emulates Mode 0
operation of an Intel 8255A Programmable Peripheral Interface (PPI)
integrated circuit. Mode 0 is one of the following three modes of
operation available with an 8255A:
●
Mode 0
-
Basic I/O; all ports are I/O ports.
●
Mode 1
-
Strobed I/O; part of Port C controls data transfer.
●
Mode 2
-
Bidirectional I/O on Port A only; part of Port C controls
data transfer.
Note:
For a complete description of the PPI operating modes, refer to an
Intel 8255A data sheet.
Your PIO-SSR Series board emulates Mode 0 only. Modes 1 and 2 are not
supported.
PIO-SSR Series boards contain 24-channel groups, as follows:
●
A PIO-SSR-24 contains one group.
●
A PIO-SSR-48 contains two groups.
●
A PIO-SSR-120 contains five groups.
The 24 digital I/O channels of a group include three 8-channel ports, as
follows: Port A, Port B, and Port C. The following section shows the I/O
addressing of these ports.
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