IAI America S-SEL-E - Manual (Page 101)

Page 96
In the past, parallel processing was accomplished by relay ladder circuitry. It was subsequently replaced by a PLC which is
equipped with micro processors. There is considerable scanning time involved in PLCs. The following shows that a PLC
scans the entire program, then sets the post if certain conditions are met.
Program Steps
3. Difference Between the Super SEL and a PLC
Real-time OS
Program 1 Program 2 • • • • • • • • • Program n
The Super SEL operating system (OS) handles programs at a high speed and executes programs only when a certain event
occurs (event driven), without scanning. Also, each parallel processing program is composed of simple one-line steps.
This makes programming and debugging easy.
With the Super SEL controller, the user will be able to develop a multi tasking program without thinking about parallel
processing, which is handled by the SEL operating system (OS).
Chapter 3. Multi-tasking