Toshiba T2N - Manual (Page 218)

5. Programming Language
User's manual 205
The instructions execution sequence in a block composed by ladder
diagram are shown below.
(1) They are executed in the sequence rung1, rung 2, rung 3 ...
through to the final rung in the block (in the case of a block with
an END instruction, through to the rung with the END instruction).
(2) They are executed according to the following rules in any one rung.
The instructions execution sequence in which function
instructions are included also follows the above rules. However,
for program execution control instructions, this will depend on the
specification of each instruction.
The following show the execution sequences in cases in which
program execution control instructions are used.
* Master Control (MCS/MCR, MCSn/MCRn)
Instruction Execution
Sequence
(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.
(4) A combination of (2) and (3)
above
When the MCS input is ON,
execution is normal.
When the MCS input is OFF,
execution is by making the
power rail from the rung
following MCS to the rung of
MCR OFF (the execution
sequence is the same).