Specifications

20
2. Replacement of FX2N series
Item
Operational difference
Caution
FX
2N series FX3U series
High-speed processing
FNC53/54/55
When the same
comparison value is set
for DHSCS, DHSCR,
and DHSZ instructions,
and interrupt process
timings are overlapped,
processing is executed
in the same order that
the instructions appear
in the program.
When the same
comparison value is set
for DHSCS, DHSCR,
and DHSZ instructions,
and interrupt process
timings are overlapped,
processing is executed
according to following
the priority order.
DHSCR(self-reset)
DHSZ
DHCT
DHSCS
DHSCR
Refer to Common caution 6 in
section 13.4 of the FX3G/FX3U/
FX3UC series programming manual
when using high-speed counter
comparison instructions.
High-speed counter
comparison applied
instructions DHSCS,
DHSCR, DHSZ.
FNC56 If an indirect device
used to store the
counting time is
changed while the SPD
instruction is being
executed, changes are
reected when the
instruction is executed
again.
If an indirect device
used to store the
counting time is
changed while the SPD
instruction is being
executed, changes
are reected after the
remaining time has
elapsed.
If having the changed counting
time being reected before the
SPD instruction is executed again
is a problem, make changes to the
device containing the counting
time before the SPD instruction is
executed.
Reection of change of
counting time during
execution of the SPD
instruction.
External FX I/O device
FNC70 to 75,77 When the number of
devices necessary for
operation is greater than
the range of devices
designated by the
operand, it is not an
error, but the arithmetic
operation is conducted
within the possible range.
When the number of
devices necessary for
operation is greater than
the range of devices
designated by the
operand, an operation
error (6706) occurs, and
the arithmetic operation
is not executed.
In the FX3U, error detection
in instruction execution is
implemented. Please check the
program, and change the device
allocation so as to avoid errors.
TKY, HKY, DSW, SEGL,
ARWS, PR instructions
FNC78/79
By turning on M8164,
the value of D8164
becomes the number of
transfer points n.
D and R devices can
be designated as the
number n of transfer
points.
For the number n of transfer points,
indirect designation of D and R
devices is possible. Please revise
the program so as to use D and R
devices.
Designation of number of
transfer points of FROM/TO
instruction
External FX device
FNC80
Because of the full
duplex interface, in the
case of one-pair wiring
with the RS command,
echo communication
occurs.
Because of the half
duplex interface, in the
case of one-pair wiring
with the RS command,
echo communication
does not occur.
In the case of one-pair wiring with the
RS command, in the FX2N, a program
for discarding the data received in
echo communication is needed, but
it is not needed in the FX3U. Delete
the program for discarding the echo
communication data.
Echo communication when
one-pair wiring is used for
RS-485 RS communication
FNC81
If M devices are
designated in S· and D·,
and the number of devices
necessary for operation
exceeds the range of
M devices, it is not an
error, but the arithmetic
operation is conducted
within the possible range.
If M devices are
designated in S· and D·,
and the number of devices
necessary for operation
exceeds the range of M
devices, an operation
error (6706) occurs, and
the arithmetic operation is
not conducted.
In the FX3U, error detection
in instruction execution is
implemented. Please check the
program, and change the device
allocation so as to avoid errors.
PRUN instructions
FNC88
S3 occupies 25 points. S3 occupies 29 points.
The number of occupied points
is increased. Conrm devices are
allocated correctly.
Increase in number of
occupied points for S3 of the
PID instruction.
Data conversion
FNC129
If the conversion result
overows, a positive
maximum value or a
negative maximum
value is stored in D·.
If the conversion result
overows, D· is not
updated, and remains at
the value before execution
of the instruction .
If the carry ag (M8022) is ON,
change the program so as to process
without referring to D·.
Operation in the event of
an overow INT instruction
execution result