Справочник Пользователя для National Instruments PC-DIO-24

This mode can be used for simple input and output operations for each of the ports.  No
handshaking is required; data is simply written to or read from a selected port.

Mode 0 has the following features:

•

Two 8-bit ports (A and B) and two 4-bit ports (upper and lower nibble 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):

•

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 of which are latched.

•

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

•

Interrupt generation and enable and/or 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.  Interrupt generation and enable and/or disable functions
are also available.  Other features of this mode include the following:

•

Used in group A only (port A and upper nibble of port C).

•

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

•

Latched inputs and outputs.

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