Omega Engineering DIGITAL INPUT/OUTPUT PCI-DIO96 - Manual (Page 15)

GROUP 0, PORT B DATA
BADR3 + 1
READ/WRITE
D0 D1 D2 D3 D4 D5 D6 D7
0 1 2 3 4 5 6 7
GROUP 0, PORT C DATA
BADR3 + 2
READ/WRITE
CL1 CL2 CL3 CL4 CH1 CH2 CH3 CH4
C1 C2 C3 C4 C5 C6 C7 C8
0 1 2 3 4 5 6 7
GROUP 0 CONFIGURE
BADR3 + 3
READ/WRITE
CL B M1 CH A M2 M3 MS
0 1 2 3 4 5 6 7
This register is used to configure the Group 0 ports as either input or output, and
configures the operating mode to mode 0, 1 or 2. The following describes
configuration for mode 0. See the Intel or Harris 8255 data sheets for information on
other modes of operation
8255 MODE 0 CONFIGURATION
1. Output Ports
In mode 0 configuration, 82C55 ports can be configured as outputs, holding the data
written to them. For example, to set all three ports (A, B, & C) of Group 0 to output
mode, write the value 80 hex to BADR3 + 3 (refer to Table 5-3 below). The user is
then able to read the current state of the output port by simply reading the address
corresponding to that port.
2. Input Ports
In mode 0 configuration, the 82C55 ports can be configured as inputs, reading the
state of the inputs lines. For example, to set all of the ports of Group 0 to the input
mode, write the value 9B hex to BADR3 + 3.
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