SMAC
LAC-26 Technical Reference Manual
4/29/2013 7
Table 2. I/O States.
Another feature of the digital input system is the ability for software input debouncing. All of the
general purpose digital inputs are automatically sampled once every millisecond. Depending on the
debounce delay set by the Input Debounce (ID) command, a given input must remain in the same state
during one or more samplings before it is considered valid. If an input were to be found in a changed state
during a sampling, the input would become invalid and the debounce delay would be restarted. If no or "0"
debounce delay is used, then no input debouncing is performed. For example: if a "ID5" command has
been issued, then a given input must remain in the same state for 5 samplings or for 5 milliseconds.
1.2.5 I/O Technical Specifications
1.2.5.1 General Purpose I/O Nominal Specifications.
Unit
Specification
5
V
Minimum voltage to activate input.
0.83
mA
Input current at minimum activation voltage.
24
V
Maximum input voltage.
4.87
mA
Input current at maximum voltage.
1.1
V
Maximum voltage to deactivate input.
6
V
Absolute maximum reverse input voltage.
40
V
Maximum voltage output can sustain.
100
mA
Maximum current output can sustain.
Table 3: General Purpose I/O Specifications
1.2.5.2 Dedicated I/O Nominal Specifications.
Unit
Specification
10
Ω
Maximum external circuit resistance to activate
input.
1
K
Ω
Minimum external circuit resistance to deactivate
input.
Table 4: Dedicated I/O Specifications
1.3 Encoder Interface
The LAC-26 has two channels of quadrature type encoder interface with optional index signal
input and the ability to 5 VDC at a minimum of 50 mA (or greater depending on other demands
put on the internal 5 VDC power supply). The phase A+ and phase B+ inputs are pulled up to +5 VDC
with 2.7K resistors, and the phase A- and phase B- inputs a biased at +2.5 VDC with 2.7K resistors. This
arrangement which will accommodate both open collector and totem pole single-ended output encoders
or differential output encoders. The phasing of the channels as well as the index signal sense can be
changed via program command.
