Specifications

Command Set 4-9
For example: A typical response from a $1DI command could be: *01FE.
This response indicates that the HI alarm is off, the LO alarm is on, DI0 = 0
and all other digital inputs are = 1
All digital inputs that are not implemented or left unconnected are read as
‘1’
Digital input 0 serves a dual function. It is both a digital input and the Event
Counter input.
When reading digital inputs with a checksum, be sure not to confuse the
checksum with the data.
Digital Output (DO)
The DO command controls eight bits of digital outputs on the module
connector. The number of digital outputs implemented depends on the
model used. The digital outputs allow the module to control external circuits
under host command. The DO command requires an argument of two hex
characters specifying the eight bits of output data.
Digital Outputs DO7 DO6 DO5 DO4 DO3 DO2 DO1 DO0
Data Bits 7 6 5 43210
The electrical implementation of the digital output consists of open-collector
transistors wired to the module connector. If a digital output is set to ‘1’ the
corresponding transistor is turned on and sinks current. Note that when a
digital output bit is set to ‘1’ the electrical output is near 0 volts. If a digital
output is set to ‘0’ the corresponding transistor is turned off and sinks no
current.
Assume a module has two digital outputs, and you wish to turn both outputs
on (sinking current). Set data bit 0 and data bit 1 to ‘1’. Since the module has
only two digital outputs, all the other bits are ‘don’t cares’. For example, this
command will turn both outputs ‘on’:
Command: $1DOFF
Response: *
To turn both outputs off you could use the command:
Command: $1DO00
Response: *
Digital outputs 0 and 1 share connector pins with the HI and LO alarms. The
Disable Alarms (DA) command is used to configure these pins as digital
outputs.
Digital output settings are not stored in nonvolatile memory. If a power failure
occurs, all digital outputs will be 0 upon power up.