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7.7 Program Execution Sequence
The instructions execution sequence is shown below.
(1) They are executed in the sequence from block 1 through the final block which contains the END instruction (or
IRET
in an interrupt program).
(2) They are executed in the sequence from rung 1 through the final rung in a block (or the END instruction).
(3) They are executed according to the following rules in any one rung.
1
When there is no vertical
connection, they are
executed from left to right.
2
When there is an OR
connection, the OR logic
portion is executed first.
3
When there is a branch, they
are executed in the order from
the upper line to the lower line.
1 2 3 4
1 2 4 6 7
3
5
1 2 3 4
5 6
4
A combination of
above.
2
and
3
1 3 4 5
2 6 8
7
The instructions execution sequence in which function instructions are included also follows the above rules. How-
ever, for program execution control instructions, such as jumps (JCS), loops
(FOR-NEXT),
subroutines (CALL-SUBR-
RET), it will depend on the specifications of each instruction.