SMAC
LAC-26 Technical Reference Manual
4/29/2013 6
1.2.3 General Purpose Outputs
Figure 3 illustrates one of the LAC-26’s general purpose outputs. These outputs are galvanically
isolated from the LAC-26. When an output is activated, positive current will flow from the collector of the
optocoupler transistor (the output pin) to it’s emitter (the output return pin),
Figure 3. LAC-26 General Purpose Output
1.2.4 Digital I/O "States"
There are several commands that deal with controlling the digital I/O. All of these commands
operate based on the following philosophy: With regard to an input, "active" means there is sufficient
current flowing through that input and "inactive" means there is lack of sufficient current through that
input. With regard to outputs, "active" means the ability for an output to pass current and "inactive" means
the inability for an output to pass current.
The Channel High (CH) and Channel Low (CL) commands provide the user with the ability to
determine whether a channel is active in the "on" state (CH) or active in the "off" state (CL). This is
analogous to a switch and to whether it is normally open or normally closed. The Channel On (CN) and
Channel Off (CF) commands do exactly as they imply in that they will turn a given output either on or off,
which will make that output either active or inactive depending on the CH and CL commands as stated
previously.
The (CH) command causes the following interpretation of the inputs and outputs:
An "activated" output is considered to be ON (e.g., Channel On “CN” command).
An "inactivated" output is considered to be OFF (e.g., Channel Off “CF” command).
An "activated" input is considered to be ON (e.g., Do If On “DN” command).
An "inactivated" input is considered to be OFF (e.g., Do If Off “DF” command).
The (CL) command causes the following interpretation of the inputs and outputs:
An "activated" output is considered to be OFF (e.g., Channel Off “CF” command).
An "inactivated" output is considered to be ON (e.g., Channel On “CN” command).
An "activated" input is considered to be OFF (e.g., Do If Off “DF” command).
An "inactivated" input is considered to be ON (e.g., Do If On “DN” command).
Input Current
“CH”
“CL”
Output Current
“CH”
“CL”
Flowing
On
Off
Flowing
CN
CF
No Flow
Off
On
No Flow
CF
CN
