National Instruments 6508 PCI-DIO-96 - Manual (Page 54)

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.
Mode 1
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.
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
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.