Cautions On Using File Registers - Mitsubishi Electric MELSEC FX3U Programming Manual

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
2) When file registers of different device numbers are specified for the source and destination
Inside built-in
memory or
memory cassette
Program
memory
Program/
comment
D1000
500 points ×
File register
14 blocks
[A]
maximum
(7000 points
maximum)
4.9.5

Cautions on using file registers

1. Cautions on using a memory cassette
When changing the contents of file registers stored in the memory cassette, confirm the following conditions:
• Set to OFF the protect switch in the memory cassette.
• 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.
*1. Only FX
2. Allowable number of writes 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).
3. Cautions on handling file registers in the same-number register update mode in BMOV (FNC
15) instruction
• When updating the contents of the same number file register, make sure that the file register number at
and
S
• Make sure that the number of transfer points specified by "n" does not exceed the file register area.
• If the number of transfer points specified by "n" exceeds the file register area, an operation error (M8067)
occurs and the instruction is not executed.
• In the case of indexing
When
S
file register area and the number of transfer points is within the file register area also.
138
Inside system
RAM
D 0
Data
memory
Data register
Write
Data register
D1400
[B]
D1499
Data register
D7999
/FX PLC
3U 3UC
are equal to each other.
D
and are indexed, the instruction is executed if the actual device number is within the
D
Write
OFF
X001
• When X001 is set to ON, the contents of the data
D1100
register area [B] are transferred to the data
register area [B] and file register area [A] as
D1199
D1400
shown in the figure on the left.
If data cannot be written to the file register area
D1499
[A] because the protect switch of the memory
cassette is ON, data is written to only the data
register area [B].
*1
4 Devices in Detail
4.9 Data Register and File Register [D]
M8024
S D
FNC 15
D1100 D1400
BMOVP
n
K100