2
Interrupt Tasks
Normally, user programs are executed in order along with the processing of the I/O Refresh etc., within the PLC processing cycle (See
"I/O Refresh").
Interrupt Tasks however are executed in precedence to this processing cycle. In the event that certain interrupt conditions are met, the processing
cycle will be suspended and the interrupt tasks will be executed first.
(The SYSMAC PLC sometimes refers to the "Interrupt Tasks" as "Interrupt Programs", but here we shall use "Interrupt Tasks", the terminology
used in the CS/CJ Series manuals)
For example, in the case of the CS/CJ Series, Interrupt Tasks can include power Off interrupt, Scheduled Interrupts, I/O Interrupts, Periodic
Interrupts based on the internal timer, and External Interrupts.
I/O Allocation
In order for user programs to utilize I/O signals from the I/O Units mounted to the PLC, it is necessary to first assign an address within the PLC I/
O Memory.
The assignment of I/O Memory to the input or output from these units within the PLC is known as I/O Allocation. The CPU Unit uses this I/O
Allocation information in the operation of I/O Refresh with connected units.
In the case of SYSMAC PLC, this I/O Allocation information is recorded in the PLC in the "Registered I/O Table". This "Registered I/O Table" can
be created by either automatically registering online with programming tools utilizing information from the unit built-in to the PLC, or by using
programming tools to design offline and then automatically registering by transmitting the I/O table to the PLC. (Some devices may not require the
creation of a Registered I/O Table, and others may not support the offline design of I/O Tables.)
●
Online Automatic Registration
●
Offline Automatic Registration
Major Interrupt Tasks
Details
Power Break Interrupt Tasks
Executed during a power break.
Scheduled Interrupt Tasks
Executed based on a specific schedule.
I/O Interrupt Tasks
Executed at the start-up of a connected Interrupt Input Unit.
External Interrupt Tasks
Executed when requests are received from the Special I/O unit, the CPU Bus Unit, and the INNER Board (only for CS
Series).
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