External Interrupts - Omron CJ2 - 02-2010 User Manual

(Interrupt Input Unit retrieval)
Interrupt task execution
Cycle execution task execution
(main program)

External Interrupts

Interrupt processing is performed at the CPU Unit in PLCs containing Special I/O Units or CPU Bus
Units. Settings do not have to be made at the CPU Unit unless the program contains an external inter-
rupt task for a particular task number. The Special I/O Unit or CPU Bus Unit must be connected in the
CPU Rack to enable external interrupts.
Receiving external interrupt tasks is always enabled. The maximum number of tasks is 256 (interrupt
task numbers 0 to 255).
Example: External Interrupt from a CJ1W-CT021 High-speed Counter Unit
CPU Unit
Cyclic task
Interrupt task
I/O memory
To communicate to the CPU Unit the status information for the two external control inputs and 32 out-
puts of this Unit for other than I/O refreshing, set the external control inputs or outputs so that they trig-
ger the external interrupt task.
Precautions for Correct Use Precautions for Correct Use
Do not use the same number for more than one interrupt task.
If an external interrupt task (0 to 255) has the same number as a power OFF task (task 1),
scheduled interrupt task (task 2 or 3), or I/O interrupt task (100 to 131), the interrupt task will be
executed for either interrupt condition (external interrupt or the other interrupt condition).
Overhead Time for External Interrupt Tasks
For external interrupt tasks, the time until the CPU Unit receives the interrupt signal depends on the
type of Unit or Board (i.e., Special I/O Unit or CJ-series CPU Bus Unit) that requests execution of the
external interrupt task from the CPU Unit and the service type of the interrupt request. For details,
refer to the relevant Unit manual.
CJ2 CPU Unit Software User's Manual
Input
Input ON delay time
I/O interrupt task
interrupt response time
Specifies
CJ1W-CT021
external interrupt
task number and
requests
interrupt
processing.
5 Understanding Programming
Ladder program
Cyclic task
execution time return time
Data
Ready for next
interrupt Input Unit retrieval
5-27
5