Mitsubishi Electric MELSEC FX3U Programming Manual page 271

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
2. Cautions on use
1) When updating the contents of a file register with a same number (same-number update mode), make
sure that the file register number is equivalent between
2) When using file registers in the same-number update mode, make sure that the number of transfer points
specified by "n" does not exceed the file register area.
3) If the file register area is exceeded while file registers are used in the same-number update mode, an
operation error (M8067) is caused and the instruction is not executed.
4) In the case of indexing (in the same-number update mode)
When
S
within the file register area and the number of transfer points does not exceed the file register area.
5) Handling of the memory cassette
When changing the contents of file registers secured inside the memory cassette, confirm the following
conditions:
- Set the protect switch of the memory cassette to OFF.
- It takes 66 to 132 ms to write data to one serial block (500 points) in the memory cassette (flash
memory). It takes 80 ms to write data to one serial block (500 points) in the memory cassette
(EEPROM).
Execution of the program is paused during this period. Because the watchdog timer is not refreshed at
this time, it is necessary to take proper countermeasures such as insertion of WDT instruction in a user
program.
6) Allowable number of times of writing to the memory
Data can be written to the memory cassette up to 10,000 times, and to the memory (EEPROM) built in
FX PLCs up to 20,000 times.
3G
When a continuous operation type instruction is used for data writing in a program, data is written to the
memory in every operation cycle of the PLC. To prevent this, make sure to use a pulse operation type
instruction (BMOVP).
7) File register operation
File registers are secured inside the built-in memory or memory cassette.
Different from general data registers, file registers can be read and written only by peripheral equipment
or BMOV (FNC 15) instruction.
and are indexing with index, the instruction is executed if the actual device number is
D
9 Move and Compare – FNC 10 to FNC 19
9.6 FNC 15 – BMOV / Block Move
and .
S D
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