AutomationDirect CLICK PLUS PLC Getting Started page 15

Step 4: Create a Project (cont'd)
Program Execution
The following is an explanation of how the CLICK PLC executes the ladder logic program that
was just entered.
The CLICK PLC executes the ladder logic program instructions, starting with Rung #1, from
left to right, and then proceeds to execute the next rung in the same fashion, carrying on
through all of the rungs in sequential order. The 6 instructions (a, b, c, d, e, and f) in the above
ladder logic program are executed in the following order.
Explanation of the Program Execution
NO (Normally Open) Contact: Address C1 and C2 are assigned to a NO Contact. C1 and
C2 are internal control bits. The internal control bits are 1 bit memory and hold the status
of ON or OFF. The contacts are enabled when the status of C1 or C2 is ON.
Timer: This instruction is used to delay an action once it is enabled. The CLICK PLC
unit can use up to 500 timers (T1 to T500) in a project. In this ladder logic program,
timer T1 is assigned. The Timer instruction is set up as an ON Delay Timer with a
5 second set point. That is, the timer status bit T1 output coil turns on 5 seconds after the
enable input of the Timer instruction turns on.
This is a NO Contact addressed as T1 and whose status is controlled by Timer T1. The
contact is enabled when Timer T1 output coil becomes true after the 5 second delay.
OUT: This is an output coil addressed as real world output Y001, which happens to be the
first output on the CLICK PLC unit. It becomes active when the T1 NO Contact in this
rung becomes enabled.
END: This is the END of the ladder logic scan, and causes the scan to start at the beginning.
CLICK PLUS PLC Hardware User Manual, 1st Edition, Rev. K – C2-USER-M
Chapter 1: Getting Started
1-15