
3. SPECIFICATIONS
3
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5
MELSEC-A
3.3.2 I/O signal details
This section explains the I/O signal ON/OFF timing and conditions.
(1) Watchdog timer error: Xn0
Turns ON if an error occurs in DN91.
OFF: Unit normal
ON:
Unit abnormal
(2) Refreshing: Xn1, Refresh request: Y(n+1)1
These signals determine whether the data in the input data area and output data area of
the buffer memory is used to refresh the network.
Refresh is conducted if the status of the master communication status area in buffer
memory is "operation in progress."
(a) To start the data refresh, turn ON refresh request (Y(n+1)1) with a sequen-ce
program.
(b) When refresh request (Y(n+1)1) is turned ON, the refresh operation starts and
refreshing (Xn1) turns ON automatically.
(c) To stop the data refresh, turn OFF refresh request Y(n+1)1 with a sequen-ce
program.
(d) The data refreshing is interrupted with "Refreshing" signal (Xn1) turned OFF
automatically and "OFF" or 0 data transmitted to all slave stations.
Refreshing the input data area still continues.
Watchdog timer error (Xn0)
Unit ready (XnF)
Refreshing (Xn1)
Refresh request (Y(n+1)1)