Common Items Between Rbfm (Fnc278) Instruction And Wbfm (Fnc279) Instruction - Mitsubishi FX3U Series Programming Manual

FX /FX Series Programmable Controllers
3U 3UC
Programming Manual - Basic & Applied Instruction Edition
31.1.1 Common items between RBFM (FNC278) instruction and WBFM (FNC279)
instruction
Specification of unit number of special function block/unit and buffer memory
1. Unit number "m1" of a special extension unit/block
Use the unit number to specify to which equipment the RBFM/WBFM instruction works.
Setting range: K0 to K7
Unit No. 0
Built-in
CC-Link/LT
FX -
3UC
32MT-LT extension
main unit block
A unit number is automatically assigned to each special extension unit/block connected to the PLC.
The unit number is assigned in the way "No. 0 → No. 1 → No. 2 ... starting from the equipment nearest the
main unit.
2. Buffer memory (BFM) number "m2"
Up to 32767 16-bit RAM memories are built in a special extension unit/block, and they are called buffer
memories.
The buffer memory number is from "0" to "32766", and the contents are determined according to each special
function unit/block.
Setting range: K0 to K32766
→ For the contents of buffer memories, refer to the manual of the used special function block/unit.
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.
M8002
0
Initial pulse
- 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.
696
number of connectable units/blocks, and handling of I/O numbers,
refer to the manual of the used PLC and special function block/unit.
Unit Unit
No. 1 No. 2
I/O Special Special
extension extension
block block
FNC 12
MOV
FNC 07
WDT
→ For the connection method of special extension units/blocks,
Unit
No. 3
I/O Special
extension extension
block block
Watchdog timer time: 300 ms
K300 D8000
Watchdog timer refresh
When WDT (FNC 07) instruction is not programmed, the value
of D8000 becomes valid during END processing.
31 Data Transfer 3 – FNC275 to FNC279
31.1 FNC278 – RBFM / Divided BFM Read