Data Translation DT300 Series, User Manual

Page: 92 / 164

Chapter 6
92
Digital I/O Features
This section describes the following features of the digital I/O subsystem:
• Digital I/O lines
• Digital I/O resolution
• Digital I/O operation modes
Digital I/O Lines
DT300 Series boards support 23 digital I/O lines through the digital input (DIN) and output
(DOUT) subsystems; DIN and DOUT subsystems use the same digital I/O lines. These lines
are divided into the following ports:
• Port A, lines 0 to 7,
• Port B, lines 0 to 7, and
• Port C, lines 0 to 6.
You can use each port for either input or output; all lines within a port have the same
configuration. For example, if you use Port A as an input port, lines 0 to 7 of Port A are
configured as inputs. Likewise, if you use Port C as an output port, lines 0 to 6 of Port C are
configured as outputs.
For fast, clocked digital input operations, you can enter the digital I/O lines from Ports A and
B as a channel in the analog input channel list; refer to
page 74 for more information.
By default, the digital I/O lines power up as digital inputs. On power up or reset, no digital
data is output from the board.
Digital I/O Resolution
For Ports A and B, you can specify the number of lines to read or write by specifying the
resolution in software. If you specify a resolution of 8, element 0 (the first subsystem)
corresponds to the Port A, lines 0 to 7; element 1 (the second subsystem) corresponds to Port
B, lines 0 to 7; and element 2 (the third subsystem) corresponds to Port C, lines 0 to 6.
If you specify a resolution of 16, element 0 corresponds to Ports A and B, lines 0 to 15; element
1 also corresponds to Ports A and B, lines 0 to 15; and element 2 corresponds to Port C, lines 0
to 6.
Note: When the resolution is 16, digital I/O lines 0 to 7 of Port B are represented as bits 8 to
15 of the digital value; do not use element 0 and element 1 at the same time.
The resolution of Port C is fixed at 7; Port C cannot be combined with Port A or B.