ISPSoft User Manual (2) Cyclic The cyclic task executes base on the setting of time interval in TASK Manager. Executing cyclic task: Priority High Cyclic task System processing Low IO : IO means I/O refresh. I/O includes local I/O points and left-side and right-side extension module data and CANopen data. The data can be specified to refresh before the set task is executed. If not specified, the data will be refreshed during the system processing. User Program: User Program stands for user program execution which is based on the execution sequences of programs assigned in a task. Remaining interval:
When the controller is to perform system processing, the low-priority task is executed first if any and then the system processing is performed. System processing: The controller will perform the system processing which includes Ethernet, RS232 and RS485 communication processing after all task requests are completed. The four terms mentioned above have the same meanings as those in the following sections. Note: If the cycle defined in the cyclic task is too short, the task will immediately repeat execution once finishing the user program but will not execute other low priority task or work on the system, and this may affect the execution on all tasks.
If the task has setup watchdog timer for program scan, this will cause response timeout by the timer and the controller will be in Error state and stops executing the user program; if the task did not setup watchdog timer for program scan, the controller will not be able to execute the system, causing problems like communication timeout. (3) Task triggered by event An event task is executed once just when the specified event happens. The timing for execution of an event task depends on the timing for occurring of the event and the priority level of the event task. Executing an event task:
Task execution condition met Priority High Tas k triggered by ev ent System processing Low 5-8 Time interval between tasks Time interval between tasks IO User program Remainin interval g IO User program Remainin interval ng System processi System processin Task execution time IO User program System pr oces IO User program System pr oces