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Appendix C Register-Level Programming
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National Instruments Corporation C-11 PC-DIO-24/PnP User Manual
outp(portc,0x56); /* Write data to port C. */
/* EXAMPLE 2*/
outp(cnfg,0x90); /* Port A is input; ports B and C are outputs. */
outp(portb,0x22); /* Write data to port B. */
outp(portc,0x55); /* Write data to port C. */
valread = inp(porta); /* Read data from port A. */
/* EXAMPLE 3 */
outp(cnfg,0x82); /* Ports A and C are outputs;
port B is an input. */
/* EXAMPLE 4 */
outp(cnfg,0x89); /* Ports A and B are outputs;
port C is an input. */
}
Mode 1—Strobed Input
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 3-bit
control/data port. The 8-bit port can be either an input or an output port,
and the 3-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
3-bit port.
The control word written to the CNFG Register to configure port A for
input in mode 1 is shown as follows. Use bits PC6 and PC7 of port C as
extra input or output lines.
D2 D1 D0D3D7
D6 D5
D4
1 = input
0 = output
Port C bits PC6 and PC7
1
0
1/0
X
X
X11