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FX2N-5A Special function block Buffer Memory (BFM) 7
7-18
7.2.9 BFM 18 hold/ reset analog output when PLC is stopped (READ/WRITE)
If BFM 18 is 0, while the PLC base unit is in Stop mode the value of BFM15 (value of BFM14 +
direct output function) will be output. If the direct output function is active, the output value will
be continuously updated, when the input channel values are changing.
If BFM18 is set to K1, and there is no TO instruction access for more than 200 ms from the
main unit to the FX
2N
-5A, consequently, the output will be stopped. In this case the last value of
BFM 15 (value of BFM14 + direct output function) will be output.
If BFM18 is set to K2, and there is no TO instruction access for more than 200 ms from the
main unit to the FX
2N
-5A, consequently, the output will be reset to the defined offset value.
If BFM18 is set to K1 or K2, a FROM/TO-Watchdog-Timer will be activated. If there is no
FROM/TO access for longer than 200ms, the action described above will be taken. (FROM/TO
Watchdog timer has barked, bit 8 of BFM18 is set.) This can be checked by monitoring BFM 18
or reading it by a FROM command. The FROM/TO Watchdog timer will automatically be reset
by a TO access to BFM 14.
The value of BFM 18 is stored non-volatile in the internal EEPROM. There is a safety function
to protect the internal EEPROM from being destroyed by accidentally writing the same value
continuously to BFM 18.