System philosophy
HARDWARE REFERENCE MANUAL
26
Revision 5.0
fig. 18
The operations executed in each CPU slot are:
In each of the three CPU slots (1, 2 and 4) the type (High or Low priority
BASIC programs or PLC) is executed which comes first in the list. Only
processes of that type will then be executed in that slot.
Example 1
Executing one High and two Low priority BASIC programs.
•
CPU slot 1: Low priority BASIC programs executed alternating
•
CPU slot 2: High priority BASIC program executed
•
CPU slot 4: High priority BASIC program executed
Special case
: in case both Low and High priority BASIC programs are
running in parallel to the PLC, CPU slot 1 executes the Low and High priority
BASIC programs alternately.
Example 2
Executing one High and two Low priority BASIC programs in parallel to the
PLC:
•
CPU slot 1: Running High and low priority BASIC programs alternately
•
CPU slot 2: PLC
•
CPU slot 4: High priority BASIC program executed
Cycle time = 2 ms
500
μ
s
1
2
3
4
CPU slot
Operation
CPU slot 1
Execute whichever comes first in the list:
•
Low priority BASIC Program, or
•
High priority BASIC Program, or
•
PLC
CPU slot 2
Execute whichever comes first in the list:
•
PLC, or
•
High priority BASIC Program, or
•
Low priority BASIC Program
CPU slot 3
System processes
CPU slot 4
Execute whichever comes first in the list:
•
High priority BASIC Program, or
•
PLC, or
•
Low priority BASIC Program
