FX Series Programmable Controllers Points Of Technique 10
10-12
In this example these three modes are
selected b
an external rotar
switch. The
rotar
switch is not connected to the PLC but
to the I/O bus on the rear of the DU unit.
The use of the rotar
switch means that the
selected modes are mutuall
exclusive in
their operation. For an operator friendl
environment the currentl
selected mode is
displa
ed on the DU screen (a
ain this could
be b
use of the DUs ASCII function).
The start/ stop controls are touch ke
s on the
DU screen. When a mode is selected the
input received at the DU unit momentaril
activates one of the followin
auxiliar
rela
s:
Rotar
switch:
position 1 'Step' - Step operation: DU input I0,
controls bit device M32 position 2 'C
cle' -
Sin
le c
cle operation:
DU input I1, controls bit device M33 position 3
'Auto' - Automatic operation: DU input I2,
controls bit device M34
Ke
assi
nment for DU screen above:
Start = M36
Stop = M37
The pro
ram run in all three mode choices is
shown opposite. As noted earlier, the 'Step'
mode will require an operator to press the
'Start' ke
to start each new STL block. This
could be viewed as an additional transfer
condition between each state. However, the
user is not required to pro
ram this as the IST
instruction controls this operation
automaticall
.
The 'C
cle' mode will process the pro
ram
from STL step S2, all the wa
throu
h until
STL step S2 is encountered a
ain. Once
more the IST instruction ensures that onl
one c
cle is completed for each initial
activation of the 'Start' input.
Finall
as su
ested b
the name, 'Auto'
mode will continuousl
c
cle throu
h the
pro
ram until the 'Stop' button is pressed.
The actual haltin
of the pro
ram c
clin
will
occur when the currentl
active c
cle is
completed.
Automatic Mode
AB
Menu
Start
Stop
Automatic Operation
Single Cycle Operation
Stepped Operation
AUTOSTEP
CYCLE
Current
Operation
messages
Rotary switch input to
DU through I/O bus
(used to select mode).
Y0
X1
T0
Y2
X2
S 2
SET Y1
M8041
M8044
T0
K10
Y3
S 20
S 21
S 22
S 23
T1
RST Y1
T1
K10
X3
Y0
S 24
X1
S 25
Y2
S 26
X2
Y4
X4
S 27
Move grip down
Clamp is active
Move grip up
Move grip right
Move grip down
Clamp is not
active
Move grip up
Move grip left
