User manual

Appendix D Register-Level Programming

National Instruments Corporation D-17 PC-DIO-96/PnP User Manual

unsigned int porta, portb, portc, cnfg;

char valread; /* Variable to store data read from a port */

/* Calculate register addresses */

porta = BASE_ADDRESS + APORTAoffset;

portb = BASE_ADDRESS + APORTBoffset;

portc = BASE_ADDRESS + APORTCoffset;

cnfg = BASE_ADDRESS + ACNFGoffset;

/* EXAMPLE 1–port A input */

outp(cnfg,0xB0); /* Port A is an input in mode 1. */

while (!(inp(portc) & 0x20)); /* Wait until IBFA is set,

indicating that data has been

loaded in port A. */

valread = inp(porta); /* Read the data from port A. */

/* EXAMPLE 2–Port B input */

outp(cnfg,0x86); /* Port B is an input in mode 1. */

while (!(inp(portc) & 0x02)); /* Wait until IBFB is set,

indicating that data has been

loaded in port B. */

valread = inp(portb);

}

Mode 1—Strobed Output

The control word written to the CNFG Register to configure port A for

output in mode 1 is shown as follows. Bits PC4 and PC5 of port C can

be used as extra input or output lines.

The control word written to the CNFG Register to configure port B for

output in mode 1 is shown as follows. Notice that port B does not have

extra input or output lines from port C.

D2 D1 D0D3D7

D6 D5

1 = input

0 = output

Port C bits PC4 and PC5

1/0

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