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FX3G/FX3U/FX3UC Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
31 Data Transfer 3 – FNC275 to FNC279
31.1 FNC278 – RBFM / Divided BFM Read
Cautions
• A watchdog timer error may occur when many numbers of points are transferred in one operation cycle. In such a
case, take either of the following countermeasures:
- Change the watchdog timer time
By overwriting the contents of D8000 (watchdog timer time), the watchdog timer detection time is changed (initial
value: K200).
When the program shown below is input, the sequence program will be monitored with the new watchdog timer
time.
- Change the number of transferred points "n2" in each operation cycle
Change the number of transferred points "n2" in each operation cycle to a smaller value.
• Do not stop the driving of the instruction while it is being executed. If driving is stopped, the buffer memory (BFM)
reading/writing processing is suspended, but the data acquired in the middle of reading/writing processing is stored
in and later and buffer memories (BFM).
• When indexing is executed, the contents of index registers at the begining of execution are used.
Even if the contents of index registers are changed after the instruction, such changes do not affect the process of
the instruction.
• The contents of "n1" devices starting from change while RBFM (FNC278) instruction is executed. After
execution of the instruction is completed, execute another instruction for "n1" devices starting from .
• Do not update (change) the contents of "n1" devices starting from while WBFM (FNC279) instruction is
executed. If the contents are updated, the intended data may not be written to the buffer memories (BFM).
• Do not update (change) the contents of "n1" buffer memories (BFM) starting from the buffer memory No. "m2" while
RBFM (FNC278) instruction is executed. If the contents are updated, the intended data may not be read.
M8002
Initial pulse
FNC 12
MOV
K300 D8000
FNC 07
WDT
Watchdog timer time: 300 ms
0
Watchdog timer refresh
When WDT (FNC 07) instruction is not programmed, the value
of D8000 becomes valid during END processing.
D
Command
input
M
{{
SET M
{{
M8029
RST M
{{
Instruction execution complete
FNC278
RBFM
m1 m2 D
n1 n2
D
D
S