FX Series Programmable Controllers Points Of Technique 10
10-13
Points of interest:
a) Users of the IST instruction will be aware that onl
one of the operation modes should be
active at one time. In this example pro
ram the isolation of 'Manual' and 'Zero return'
modes b
the use of separate DU control screens, and the use of a rotar
switch to
isolate the three automatic modes achieves this ob
ective. Alternativel
all of the
operation modes could be selected b
a rotar
switch.
b) For users who would like to test this example usin
simulator switches (i.e., without usin
a data access unit) the appropriate pro
ram chan
es are noted next to the full pro
ram
listin
later in this section. Alternativel
, the ori
inal pro
ram could be used with all of the
input conditions bein
iven b
forcin
ON the contacts with a pro
rammin
device e.
.
a hand held pro
rammer, Medoc etc.
c) Special fla
s used in this pro
ram are:
• M8040: State transfer inhibit
- Manual mode: Alwa
s ON.
Zero return and C
cle modes: Once the 'Stop' input is
iven the current state is
retained until the 'Start' input is received.
Step mode: This fla
is OFF when the 'Start' input is ON. At all other times M8040 is
ON, this enables the sin
le STL step operation to be achieved.
Auto mode: M8040 is ON initiall
when the PLC is switched into RUN. It is reset
when the 'Start' input is
iven.
• M8041: State transfer start
- Manual and Zero return modes: This fla
is not used.
Step and C
cle modes: This fla
is onl
active while the 'Start' input is received.
Auto mode: The fla
is set ON after the 'Start' input is received. It is reset after the
'Stop' input is received.
• M8042: Start pulse
- This is momentaril
active after the 'Start' input is received.
• M8043: Zero return complete
- This is a user activated device which should be controlled within the users pro
ram.
• M8044: At Zero position/ condition
- This is a user activated device which should be controlled within the users pro
ram.
