FX Series Programmable Controllers STL Programming 3
3-7
3.5 Rules and Techniques For STL programs
It can be seen that there are a lot of advanta
es to usin
STL st
le pro
rammin
but there are
a few points a user must be aware of when writin
the STL sub-pro
rams.
These are hi
hli
hted in this section.
3.5.1 Basic Notes On The Behavior Of STL programs
• When an STL state becomes active its pro
ram is processed until the next step is tri
ered.
The contents of the pro
ram can contain all of the pro
rammin
items and features of a
standard ladder pro
ram, i.e. LoaD, AND OR, OUT, ReSeT etc., as well as applied
instructions.
• When writin
the sub-pro
ram of an STL state, the first vertical ‘bus bar’ after the STL
instruction can be considered in a similar manner as the left hand bus bar of a standard lad-
der pro
ram.
• In normal pro
rammin
usin
dual coils is not an acceptable technique. However repetition
of a coil in separate STL pro
ram blocks is allowed.
STL
S005
Y000
Y011
Y014
RET
X001
X000
X012
X013
1
Each STL step makes its own bus bar. This
means that a user, cannot use an MPS
instruction directl
after the STL instruction
(see ), i.e. There needs to be at least a
sin
le contact before the MPS instruction.
Note:
Usin
out coils and even applied
instructions immediatel
after an STL
instruction is permitted.
This is because the user can take advanta
e of the STL’s
unique feature of isolatin
all STL steps except the active
STL steps.
This means in practice that there will be no conflict between
dual coils. The example opposite shows M111 used twice in a
sin
le STL flow.
Caution:
The same coil should NOT be pro
rammed in steps
that will be active at the same time as this will result in the
same problem as other dual coils.
