CPU ADAM 821x
Chapter 1 Principles
ADAM 8000 Manual CPU 821x – Rev 1.1
1-13
Operating modes of a CPU
These CPUs are intended for small and medium sized applications and are
supplied with an integrated 24V power supply. The CPU contains a
standard processor with internal program memory. In combination with the
System 82xx peripherals the unit provides a powerful solution for process
automation applications within the System 82xx family.
A CPU supports the following modes of operation:
•
cyclic processing
•
timer processing
•
alarm controlled processing
•
priority based processing
Cyclic
processing represents the major portion of all the processes that are
executed in the CPU. Identical sequences of operations are repeated in a
never ending cycle.
Where a process requires control signals at constant intervals you can initiate
certain operations based upon a
timer
, e.g. not critical monitoring functions
at one-second intervals.
If a process signal requires a quick response you would allocate this signal
to an
alarm controlled
procedure. An alarm may activate a procedure in
your program.
The above processes are handled by the CPU in accordance with their
priority
. Since a timer or an alarm event requires a quick reaction the CPU
will interrupt the cyclic processing when these high-priority events occur to
react to the event. Cyclic processing will resume once the reaction has
been processed. This means that cyclic processing has the lowest priority.
General
Cyclic processing
Timer processing
Alarm controlled
operation
Priority based
processing
