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Appendix C Register-Level Programming
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National Instruments Corporation C-21 PC-DIO-24/PnP User Manual
Main() {
#define BASE_ADDRESS 0x180 /* Board located at address 180 */
#define PORTAoffset 0x00 /* Offset for port A */
#define PORTBoffset 0x01 /* Offset for port B */
#define PORTCoffset 0x02 /* Offset for port C */
#define CNFGoffset 0x03 /* Offset for CNFG */
#define IREG1offset 0x14 /* Offset for Interrupt Reg. 1 */
#define IREG2offset 0x15 /* Offset for Interrupt Reg. 2 */
unsigned int porta, portb, portc, cnfg, ireg1, ireg2;
char valread; /* Variable to store data read from a port */
/* Calculate register addresses */
porta = BASE_ADDRESS + PORTAoffset;
portb = BASE_ADDRESS + PORTBoffset;
portc = BASE_ADDRESS + PORTCoffset;
cnfg = BASE_ADDRESS + CNFGoffset;
ireg1 = BASE_ADDRESS + IREG1offset;
ireg2 = BASE_ADDRESS + IREG2offset;
/* EXAMPLE 1–Set up interrupts for mode 1 input for port A. Enable the
appropriate interrupt bits. */
outp(cnfg,0xB0); /* Port A is an input in mode 1. */
outp(cnfg,0x09); /* Set PC4 to enable interrupts from 82C55A. */
outp(ireg1,0x01); /* Set IRQ0 to enable port A interrupts. */
outp(ireg2,0x04); /* Set INTEN bit. */
/* EXAMPLE 2–Set up interrupts for mode 1 input for port B. Enable the
appropriate interrupt bits. */
outp(cnfg,0x86); /* Port B is an input in mode 1. */
outp(cnfg,0x05); /* Set PC2 to enable interrupts from 82C55A. */
outp(ireg1,0x02); /* Set IRQ1 to enable port B interrupts. */
outp(ireg2,0x04); /* Set INTEN bit. */
/* EXAMPLE 3–Set up interrupts for mode 1 output for port A. Enable the
appropriate interrupt bits. */
outp(cnfg,0xA0); /* Port A is an output in mode 1. */
outp(cnfg,0x0D); /* Set PC6 to enable interrupts from 82C55A. */
outp(ireg1,0x01); /* Set IRQ0 to enable port A interrupts. */
outp(ireg2,0x04); /* Set INTEN bit. */
/* EXAMPLE 4–Set up interrupts for mode 1 output for port B. Enable the
appropriate interrupt bits. */
outp(cnfg,0x84); /* Port B is an output in mode 1. */
outp(cnfg,0x05); /* Set PC2 to enable interrupts from 82C55A. */