
B–61863E/15
2. SEQUENCE PROGRAMPMC SEQUENCE PROGRAM
57
The exact sequence processing time is displayed on the CRT screen when
the sequence programs have been completed. The time is 2nd level
sequence division number n x 8 ms.
This section explains how to estimate processing times that are important
in sequence control when the ladder diagram, the basis of sequence
program control, is almost complete.
(1) Processing time calculation units
Sequence processing time estimation is based on the basic
instructions (AND, OR, etc.). The execution time for a functional
instruction is given in the execution constant column of the
Functional Instruction Table. Converted to a basic instruction; that
is the number of basic instructions that a functional instruction is
equivalent to.
Processing time is determined for the above using the equation in
item below.
(2) Processing time estimation equation
The number of division (n) in the 2nd level sequence is determined
and the processing time is calculated using the following equations:
Sequence processing time =
n (number of division) 8 msec
(LT) µsec
n=
(ET)µsec – (HT)µsec
+1
(n is an integer, fractions are omitted)
(a) (HT) is the execution time for the 1st level sequence section.
(HT)={(number of steps in basic instruction)+(sum of functional
instruction execution time constants) 10} (IT) µsec
Execution time constant for END.1 (206) must be included in HT.
(b) (LT) is the execution time for the 2nd level sequence section.
(LT)={(number of steps in basic instruction)+(sum of functional
instruction execution time constants) 10} (IT) µsec
END.2 execution time (127) must be included.
(c) (ET) is the execution time assigned to the 1st and 2nd level parts
out of 8 ms.
For PMC–SB
(ET) = 1.25 ms = 1250µs
For PMC–SC (standard setting when LADDER EXEC = 100%)
(ET) = 5 ms = 5000µs
(d) IT) is the execution constant for calculating the processing time.
The value is as follows:
(IT) = 0.15µs
2.7
SEQUENCE
PROGRAM
PROCESSING TIME