Data Translation DT9850 Series, User Manual, Page: 38 / 104

Chapter 3
38
Connecting Digital I/O Signals
This section describes how to configure the digital input signals for pull-up or pull-down,
how to wire digital inputs, and how to wire digital outputs.
Configuring the State of the Digital Input Signals
By default, the digital input signals are floating when unwired. Using the Digital I/O
Termination Select pin (TB1, pin 19), you can configure the digital input signals to be pulled
up (high value) or to be pulled down (low value) when unwired. If you are using the
interrupt-on-change feature, you must configure the state of the input lines or you will see
unwanted transitions.
Figure 8 shows how to configure the digital I/O signals for pull-up; Figure 9 shows how to
configure the digital I/O signals for pull-down.
Figure 8: Configuring the Digital Input Signals for Pull-Up (High Value)
Figure 9: Configuring the Digital Output Signals for Pull-Down (Low Value)
+5V Out
Digital I/O Termination Select
20
19
DT9850 Series
Module
Digital Ground
Digital I/O Termination Select
23
19
DT9850 Series
Module
Note that you could connect pin 19 to any
digital ground (pin 23 or 32) to pull down the
Digital I/O Termination Select pin to 0 V.