ABB CL Series Applications Manual page 191

Wiring with the logic relay
188
I1um7----ÄM8
h------ÄM7
M8uM3----SM4
dm3----RM4
dM2----SM3
dm2----RM3
dM1----SM2
dm1----RM2
dI2----SM1
hi2----RM1
I3------uRM1
dRM2
dRM3
hRM4
Figure 76: CL circuit diagram shift register
How does the shift register work?
The shift pulse is activated for exactly one cycle. To do this,
the shift pulse is generated by evaluating the change from I1
OFF to I1 ON – the rising edge.
The cyclical processing of the logic relay is used to trigger the
shift pulse.
When I1 is activated for the first time, the marker relay
n/c contact M7 is closed during the first pass through the
cycle. Thus, the series circuit consisting of I1, n/c contact M7
(closed) and M8 is activated. Although M7 is now also
activated, this does not yet have any effect on contact M7.
The contact of M8 (n/o contact) was still open during the first
cycle so a shift pulse cannot yet be generated. When the
relay coil M8 is activated, the logic relay transfers the result
to the contacts.
In the second cycle n/c contact M7 is open. The series circuit
is opened. The contact M8 is activated from the result of the
first cycle. Now, all the storage locations are either set or
reset in accordance with the series circuit.
1SVC 440 795 M0100
Generate shift pulse
Set 4th storage location
Clear 4th storage location
Set 3rd storage location
Clear 3rd storage location
Set 2nd storage location
Clear 2nd storage location
Set 1st storage location
Clear 1st storage location
Clear all storage locations