Mitsubishi Electric MELSEC-A User Manual page 152

15. MULTIDROP LOCAL STATION
MELSEC-A
(a) 1 (master): 1 (slave) ratio and SW22 off
Error occurrence
AJ71 UC24
transmission
scan
XnO
sequence
1) The error switches XnO off and Xn2 on.
2) Xn2 automatically switches off on normal completion of the re-
started pre-transmission sequence.
3) XnO switches on after completion of the first restarted data trans-
mission sequence.
When an error occurs during the data transmission sequence, the
received data area is not cleared.
(b) AJ71 UC24 as local station n and master station SW22 on (n
=
3)
Station 1
Station 2
Station
3
Xn3
(Master station)
I
XnO
I
(3rd station)
,
1 f
I
Xn2
(3rd station)
f
Faulty slave station re-
L
turn request
If an error occurs during the data transmission sequence ((C)) with
station 3. the master station s t o ~ s communication with station
3
and initiates the data transmission sequence with station 1 ((D)).
Approx. 500 ms after the return request is given from the master
station, the pre-transmission sequence is initiated at station 3. If
this is completed without fault, then the data transmiss~on se-
quence ((J)) is restarted.
1) The error switches XnO off and Xn2 on.
2)
XnO switches on, Xn2 switches off when the data transmission
sequence is completed ((J)) after the pre-transmission sequence
at station 3.