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Chapter 6 Programming
PCI-DIO-96 User Manual 6-10
©
National Instruments Corporation
Mode 0 Basic I/O Programming Example
The following example shows how to configure PPI A for mode 0 input
and output.
Write (8255Cnfg,0x80) Set mode 0—ports A, B, and C
are outputs
Write (PortA, Data) Write data to port A
Write (PortB, Data) Write data to port B
Write (PortC, Data) Write data to port C
Write (8255Cnfg,0x90) Set mode 0—port A is Input;
ports B and C are outputs
Write (PortB, Data) Write data to port B
Read (PortA) Read data from port A
Mode 1–Strobed Input
Note: For mode 1 examples, you must configure the don’t care bits appropriately
in the control word if you want to use the other ports in combination with
the example.
In mode 1, the digital I/O bits are divided into two groups: group A and
group B. Each of these groups contains one 8-bit port and one 4-bit
control/data port. The 8-bit port can be either an input or an output port,
and the 4-bit port is used for control and status information for the 8-bit
port. The transfer of data is synchronized by handshaking signals in the
4-bit port.
The control word written to the Configuration Register to configure
port A for input in mode 1 is shown in Figure 6-1. You can use bits PC6
and PC7 of port C as extra input or output lines.
Figure 6-1. Control Word to Configure Port A for Mode 1 Input
Port C bits PC6 and PC7
1 = Input
0 = Output
D7 D6 D5 D4 D3 D2 D1 D0
10111/0X XX