National Instruments PC-DIO-24, User Manual

Page: 39 / 75

Chapter 4 Register-Level Programming
© National Instruments Corporation 4-9 PC-DIO-24 User Manual
Mode 1 Input Programming Example
Main() {
#define BASE_ADDRESS 0x210 /* Board located at address 210. */
#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 */
register unsigned int porta, portb, portc, cnfg;
char valread;
/* Variable to store data read from a
port */
/* Calculate register addresses. */
porta = BASE_A PORTAoffset;
portb = BASE_A PORTBoffset;
portc = BASE_A PORTCoffset;
cnfg = BASE_A CNFGoffset;
/* 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 when
port A uses mode 1 output.
1 0 1 0 1/0 X X X
7 6 5 4 3 2 1 0
1 = input
0 = output
Port C bits PC4 and PC5