Register-Level Programming Chapter 4
PC-DIO-96 User Manual 4-10 © National Instruments Corporation
Mode 2
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.
Single Bit Set/Reset Feature
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.
Mode 0—Basic I/O
Mode 0 can be used for simple I/O functions (no handshaking) for each of the three ports. Each
port can be assigned as an input or an output port. The 16 possible I/O configurations are shown
in Table 4-3. Notice that bit 7 of the control word is set when programming the mode of
operation for each port.