Introduction
One of the best ways to improve PLC programming skills is to stop thinking only in terms of individual instructions and start thinking in terms of process behavior, equipment states, …
Read MoreA PLC program can work perfectly and still be difficult to troubleshoot.
That distinction matters.
When we first learn ladder logic, the goal is usually simple:
Make the motor run.
Later, the goal becomes …
Read MoreOne of the most useful PLC programming patterns a technician can learn is also one of the simplest:
Trigger → Hold-In → Interrupt
The idea is straightforward.
Something starts the action.
Something keeps it …
Read MoreIn industrial PLC programming, there are often several ways to make the same machine work.
Two of the most common methods for maintaining a control condition are Seal-In logic and Latch/Unlatch …
Read MoreWhen working with Allen-Bradley ControlLogix or CompactLogix systems, one of the first architectural decisions a programmer eventually faces is how to handle physical I/O inside the PLC program.
At the beginning, …
Read MoreIn the first article of this series, we introduced the idea of separating physical PLC I/O from application logic.
Now we can address one of the most common questions in Allen-Bradley …
Read MoreIn the previous article, we compared three common ways of representing PLC I/O:
Direct physical I/O
Alias Tags
Mapped controller tags
Now it is time to build the mapping layer itself.
For digital signals, one …
Read MoreIn the previous article, we built an I/O mapping layer using individual instructions.
For digital signals, we used logic such as:
XIC Physic
al_Input
OTE Internal_Tag
For numeric values, we introduced:
MOV Source Destination
This approach is …
Read MoreIn the previous articles, we built an I/O architecture using:
Direct physical I/O
Alias Tags
Individual mapped tags
XIC/XIO and OTE
MOV
COP
CPS
These methods allow us to separate physical hardware from application logic.
But as the machine …
Read MoreIn the previous articles, we explored several ways to organize and transfer PLC data:
Direct I/O
Alias Tags
Individual Mapping
MOV
COP
CPS
UDT-Based Architecture
Now we can bring those concepts together and build a complete digital I/O …
Read More