Ist Instruction Equivalent Circuit - Mitsubishi Electric MELSEC FX3U Programming Manual

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition

14.1.1 IST instruction equivalent circuit

The details of special auxiliary relays (M) and initial state relays (S0 to S9) which are automatically controlled
by IST instruction are as shown in the equivalent circuit below. (Refer to the equivalent circuit below for
reference.) This equivalent circuit cannot be programmed.
1. Equivalent circuit
Continuous
operation
X024 M8041
X026 Automatic start
X026 Automatic start
Zero return start
X025
X020 Individual operation
Zero
return X027
X021
X022Stepping operation
X023 Cycle
X027 Stop
operation
M8002 Initial pulse
M8040 Self-holding
M8000 RUN monitor
Individual
X020
operation
X021 Zero return
X022 to X024 M8043
Automatic Zero return
complete
operation
*1. Because the above equivalent circuit is provided only for explanation, it cannot be actually programmed.
2. Switching of the operation mode
When the operation mode is switched among the individual operation, zero return operation and automatic
operation, all outputs and conventional states are reset at one time unless the machine is located in the zero
point. (Reset of all outputs
S1
Zero return
X021
S2
Automatic
X022 to X024
Individual
operation
X020
S2
Automatic
X022 to X024
Even if the mode is switched from automatic operation to zero return operation while S2 is ON, state relays
(except initial state relays) and outputs are not reset.
*1. All outputs: Outputs (Y) not driven by state relays
OUT and SET instructions
Stepping
X027
X022
operation
Cycle
Stop
X023
operation
Continuous
X024
operation
X020
Individual
operation
Stop
M8042
Start pulse
*1
M8044
S 0
Zero point
condition
*1
X025
S 1
Zero return
start
*1
M8041
S 2
Transfer start
*1
is not executed when M8045 is driven.)
M8043
Switched
Zero return
to X020
complete
(individual
operation)
Switched
to X021
(zero
return
operation)
14 Handy Instruction – FNC 60 to FNC 69
M8041 is set to ON when the start button
M8041
is pressed in the automatic mode.
Especially in the continuous mode,
Transfer
M8041 holds its status by itself, and is
start
reset when the stop button is pressed.
*1
PLS M8042
Start pulse
M8040 is set to ON in the stepping
M8040
mode, and set to OFF every time the
start button is pressed.
STL transfer
In the zero return operation or cycle
disable
operation, M8040 holds its status by
itself when the stop button is pressed,
and is reset when the start button is
pressed.
M8047
Enable STL monitoring
The initial state is switched according to
M8043
each mode input, and M8043 is
Zero return
controlled at the same time.
complete
However, it is necessary to control
M8044 and M8043 in user programs
RST M8043
also.
Zero return
complete signal is
reset
Conventional states and
corresponding outputs are
reset at one time.
All output reset disable
When M8045 is OFF, all
outputs are reset.
and outputs (Y) driven by state relays
D S
1
14.1 FNC 60 – IST / Initial State
D S
1
407
11
12
13
14
15
16
17
18
19
20
in