Specifications

Digital I/O Functions 6-2
connection to a logic input is shown in Figure 6.2. In some cases, the
common-mode voltage of the GND terminal may be significantly different
from the ground potential of the logic input to be interfaced. This may
occur when the module is powered remotely. In this case, an opto-isolator
may be used to eliminate the common-mode voltage. See Figure 6.2. In all
cases, the current switched by the transistor may not be more than 30mA.
Only three commands can effect the Digital Output. The Enable Alarms
(EA) and Disable Alarms (DA) commands select the function of the DOØ/
LO and DO1/HI pin outputs. To route digital outputs to these pins, use the
Disable Alarms (DA) command. The Enable Alarms (EA) command con-
figures these two pins as alarm outputs. The Enable Alarms and Disable
Alarms commands do not affect the other digital outputs, DO2-DO7. The
digital outputs are controlled by the host with the Digital Output (DO)
command.
If the module loses power, the digital outputs are turned off. The outputs
will remain off until switched by a Digital Output (DO) command. The
function of the shared pins, DOØ/LO and DO1/HI is not affected if power is
lost, since this information is stored in nonvolatile memory.
The digital outputs are not affected by the Remote Reset (RR) command.
Digital Inputs
Figure 6.2 Digital Outputs Used With Logic