Specifications

18
2. Replacement of FX2N series
2.4 Program conversion
2.4.1 Cautions for program change
z Operational difference of FX2N series and FX3U series
The FX
3U series can use the same instructions used in the FX2N series, but the following operations are
different. Depending on the hardware conguration or program contents, check the corresponding items
by correcting or replacing the sequence program or checking operations.
 Operational difference and cautions about program and system
Item
Operational difference
Caution
FX
2N series FX3U series
System related
Initial setting
When DC power supply
type is used
Initial setting of D8008
Program for writing -1
in D8008 is needed for
initialization.
Not needed because
the system is initialized
automatically.
FX3U DC power supply type does
not require initialization of D8008.
Please delete the initial setting
program.
Devices monitored by M8004
for error detection
M8060 to M8067,
except for M8062.
M8060 to M8067,
except for M8062 and
M8063.
If M8004 is used to monitor
M8063, add an additional program
to provide equivalent operation.
High-speed input
32-bit counter specied in
single word instruction
If double words C200
to C255 are specied in
a single word applied
instruction, an operation
error occurs when the
command is executed.
If double words C200
to C255 are specied in
a single word applied
instruction, RUN is not
executed, and a syntax
error occurs. However,
the ZRST command can
designate C200 to C255.
In FX3U, error detection before
RUN is implemented.
Check the program, and correct so
as to avoid errors.
Pulse catch function
After the EI command
is executed, the pulse
catch function is made
valid.
If there is EI command
in the sequence
program, the pulse catch
function is always valid.
In FX
3U, the pulse catch function is
valid even in DI state.
Communication
Clear timing for serial
communication error M8063
and D8063 devices.
When changed from
STOP to RUN.
When power is turned
OFF.
Not cleared when changed from
STOP to RUN; when necessary to
clear, add an initializing program
using the RST command.
Parallel link
Baud rate 19,200bps 115,200bps
It must be noted that there is an
increased possibility of noise with
faster communication speeds.
Link time
of ordinary
parallel link
mode
70ms
+master station
operation period (ms)
+slave station operation
period (ms)
15ms
+master station
operation period (ms)
+slave station operation
period (ms)
Since the link time becomes shorter,
conrm the update timing of the
link device.
Link time of
high-speed
parallel link
mode
20ms
+master station
operation period (ms)
+slave station operation
period (ms)
5ms
+master station
operation period (ms)
+slave station operation
period (ms)
Instruction related
Step ladder program
STL instruction in transfer
and recombination
programs.
If a NOP instruction is
inserted between STL
instructions, transfer
and recombination are
not enabled.
If a NOP instruction is
inserted between STL
instructions, transfer
and recombination are
enabled.
If a NOP instruction is inserted
between STL instructions, replace
it with a dummy program not
containing the NOP instruction and
having no effect on the sequence
operation.
ON condition of STL
operation device M8046.
If S0 to S899 is ON and
M8047 is enabled.
If S0 to S899, S1000
to S4095 is ON when
M8047 is enabled.
Since the object device range
differs, add a program for
initializing S1000 to S4095.