Rockwell Automation 1760-xxxx Pico Controller User Manual - Manual (Page 158)

Publication 1760-UM001D-EN-P - September 2005
7-8 Retention
The circuit above functions in the same way as an impulse relay
switch. The make contact remains switched on in the first Pico cycle
if:
• a coil is actuated by the make contact of a retentive marker
(series and parallel connection both apply here too), and
• when the power is switched on, the reset condition for this
retentive marker is on.
The enable time, T2, prevents Q1 from flickering.
Retentive Timing Relays Use of Retention
The retentive timing relays T7 and T8 can be operated retentively in
all six different switching functions. The retention setting only works
under certain conditions for the switching functions. These can be
subdivided into groups 1 and 2.
If these conditions are not fulfilled, the actual value is cleared when
the power is restored. If the R coil (Reset) is actuated, the actual value
is also cleared.
Retention with Group 1
Requirement:
When power is applied to Pico, actuated trigger coils TT7, TT8 can
retain their state '1' (switched on) until the preset time period has
elapsed. This can be implemented using retentive markers or inputs
connected to power.
Retention with Group 2
Requirement:
When power is applied to Pico, actuated trigger coils TT7 and TT8 can
retain their state '0' (switched off) until the preset time period has
elapsed. This can be implemented using retentive markers or inputs
connected to power.
Group Retentive Function
Group 1 On-delayed
On-delayed switching with random range
Single-pulse
Flashing
Group 2 Off-delayed
Off-delayed switching with random time range