Rockwell Automation 1772-L8_LW_LWP_LX_LXP,D17726.5.8 User Manual - Manual (Page 399)

Programming Technique
Chapter 25
25-9
This application illustrates the program control instructions, master control
reset (MCR) and zone control last state (ZCL) (Figure 25.8).
Figure 25.8
Program Control
110
17
MCR
ZCL
110
16 15
011
MCR
Master Control Reset
110
17
ZCL
110
16 15
011
Zone Control Last State
Before you program these two instructions, you must think about how you
would want outputs to react when you change the process or operation.
Using the MCR instruction, rung logic shows:
If bit 110/17 is false, then bit 011/15 is energized if 110/16 is set. This
is normal operation.
If bit 110/17 is true, then bit 011/15 is reset regardless of the state of
110/16. All outputs within an MCR zone are reset when the zone is
disabled (start fence is false).
Using the ZCL instruction, rung logic shows:
If bit 110/17 is false, then bit 011/15 is energized if 110/16 is set. This
is normal operation.
If address 110/17 is true, then bit 011/15 is left in its last state regardless
of the state of 110/16. All outputs within a ZCL zone are left in their
last state when the zone is disabled (start fence is false).
Program Control