National Instruments PC-DIO-96 Manual Do Utilizador

outp(cnfg,0xA0);

/* Port A is an output in mode 1.*/

while (!(inp(portc) & 0x80));

/* Wait until OBFA* is set, indicating

that the data last written to port A
has been read.*/

outp(porta,0x12);

/* Write data to port A. */

/* EXAMPLE 2–port B output */

outp(cnfg,0x84);

/* Port B is an output in mode 1.*/

while (!(inp(portc) & 0x02));

/* Wait until OBFB* is set, indicating

that the data last written to port B
has been read.*/

outp(portb,0x34);

/* Write the data to port B. */

}

Mode 2 has an 8-bit bus that can transfer both input and output data without changing the
configuration.  The data transfers are synchronized with handshaking lines in port C.  This mode
uses only port A; however, port B can be used in either mode 0 or mode 1 while port A is
configured for mode 2.

The control word written to the CNFG Register to configure port A as a bidirectional data bus in
mode 2 is shown as follows.  If port B is configured for mode 0, then PC2, PC1, and PC0 of port
C can be used as extra input or output lines.

D2

D1

D0

D3

D7

D6

D5

D4

1 = input
0 = output

Port C
(PC2-PC0)

1

1/0

X

X

X

1

1 = input
0 = output

Port B

0 = mode 0
1 = mode 1

Group B Mode

1/0

1/0

During a mode 2 data transfer, the status of the handshaking lines and interrupt signals can be
obtained by reading port C.  The port C status-word bit definitions for a mode 2 transfer are
shown as follows.