Appendix C Register-Level Programming
PC-DIO-24/PnP User Manual C-14
©
National Instruments Corporation
/* 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 portB for
output in mode1 is shown as follows. Notice that port B does not have
extra input or output lines left from portC when ports A andB are both
enabled for handshaking.
During a mode 1 data write transfer, the status of the handshaking lines
and interrupt signals can be obtained by reading port C. Notice that the
bit definitions are different for a write and a read transfer.
D2 D1 D0D3D7 D6 D5 D4
1 = input
0 = output
Port C bits PC4 and PC5
101/0 XXX10
D2 D1 D0D3D7 D6 D5 D4
1XXX11X
X