Справочник Пользователя для National Instruments PCI-DIO-96

Chapter 6

Programming

PCI-DIO-96 User Manual

6-8

 National Instruments Corporation

Mode 0 has the following features:

•

Two 8-bit ports (A and B) and two 4-bit ports (upper and lower 
nibbles of port C).

•

Any port can be input or output.

•

Outputs are latched, but inputs are not latched.

This mode transfers data that is synchronized by handshaking signals. 
Ports A and B use the eight lines of port C to generate or receive the 
handshake signals. This mode divides the ports into two groups 
(group A and group B) and includes the following features:

•

Each group contains one 8-bit data port (port A or port B) and one 
4-bit control/data port (upper or lower nibble of port C). 

•

The 8-bit data ports can be either input or output; both are latched. 

•

The 4-bit ports are used for control and status of the 8-bit data ports.

•

Interrupt generation and enable/disable functions are available.

This mode can be used for communication over a bidirectional 8-bit 
bus. Handshaking signals are used in a manner similar to mode 1. 
Mode 2 is available for use in group A only (port A and the upper 
nibble of port C). Other features of this mode include the following:

•

One 8-bit bidirectional port (port A) and a 5-bit control/status port 
(port C).

•

Latched inputs and outputs.

•

Interrupt generation and enable/disable functions.

Any of the eight bits of port C can be set or reset with one control word. 
This feature generates control signals for port A and port B when these 
ports are operating in mode 1 or mode 2.

You can use mode 0 for simple I/O functions (no handshaking) for each 
of the three ports and assign each port as an input or an output port. 
Table 6-2 shows the 16 possible I/O configurations. Notice that bit 7 of 
the control word is set when programming the mode of operation for 
each port.