Allen-Bradley Micro830, Руководство пользователя

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Rockwell Automation Publication 2080-UM002K-EN-E - March 2019
Chapter 6 Program Execution in Micro800
In addition to the User Fault Routine, Micro800 controllers also support two
Selectable Timed Interrupts (STI). STIs execute assigned programs once every
set point interval (1…65535 ms).
The Global System Variables associated with cycles/scans are:
•
__SYSVA_CYCLECNT – Cycle counter
•
__SYSVA_TCYCURRENT – Current cycle time
•
__SYSVA_TCYMAXIMUM – Maximum cycle time since last start.
Execution Rules
This section illustrates the execution of a program. The execution follows four
main steps within a loop. The loop duration is a cycle time for a program.
When a cycle time is specified, a resource waits until this time has elapsed before
starting the execution of a new cycle. The POUs execution time varies depending
on the number of active instructions. When a cycle exceeds the specified time, the
loop continues to execute the cycle but sets an overrun flag. In such a case, the
application no longer runs in real time.
When a cycle time is not specified, a resource performs all steps in the loop then
restarts a new cycle without waiting.
Optional Module
Normally before the read inputs step, the controller will verify the presence of any
configured plug-in and expansion I/O modules. If a plug-in or expansion I/O
module is missing, the controller will fault. In Connected Components
Workbench software release 10 or later, an Optional Module configuration
option is added to prevent a missing plug-in I/O or expansion I/O module from
faulting the controller if enabled. This option can be enabled separately for each
plug-in I/O or expansion I/O module.
1.
Read inputs
2.
Execute POUs
(1)
/programs
3.
Write outputs
4.
Housekeeping (data log,
recipe, communications)
(1) Program Organizational Unit.
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