Writing An Interrupt Rll Program; Basic Outline Of Interrupt Processing - Siemens SIMATIC 505 User Manual

Writing an Interrupt
RLL Program
Basic Outline of
Interrupt
Processing
SIMATIC 505 Interrupt Input Module User Manual
In order to take advantage of the Interrupt feature of this module, you must
write a Relay Ladder Logic (RLL) program that contains the appropriate
logic to execute the required response to interrupts generated by this
module. For a more detailed description of the requirements and operation
of the interrupt RLL program, refer to the SIMATIC TI545/TI555 System
Manual (PPX:545/555–8101–2) and the SIMATIC TI505 Programming
Reference Manual (PPX:505–8104–5).
The Interrupt Input Module and the CPU work together to process
interrupt signals in the following manner.
1. When a field signal connected to an interrupt input transitions in a
manner that matches the interrupt type selected for that input, the
module sets the corresponding interrupt status input point and
generates an interrupt to the CPU.
2. The CPU detects this interrupt, and, if proper qualifying conditions are
met, executes the interrupt RLL program, provided the CPU is in Run
Mode.
3. The CPU automatically issues a rearm signal to the module to clear the
current interrupt event and to allow new events.
4. If an interrupt transition occurs at a given input point while the CPU is
currently processing an interrupt event, the module holds the new
event until the CPU issues the rearm signal to complete processing of
the current event. The module then generates another interrupt to
signal the CPU that a new event has occurred.
NOTE: If an interrupt transition occurs at an input point while the module
is holding an event from the same input point, the new event will effectively
be lost, since the module will only generate a single interrupt to the CPU.
This behavior is significant only in pulse-counting applications, where
pulses could potentially be missed if the pulse frequency is too high. Refer to
your CPU's Release Notes for specifications on execution times.
Operating the Module 3-3