Rockwell Automation 1772-LS_LSP,D17726.8.6 PROG/OPER MANUAL-MINI PLC-2/05 - Manual (Page 216)

Programming Techniques
Chapter 18
18-8
This application illustrates the program control instructions, master control
reset (MCR) and zone control last state (ZCL) (Figure 18.8).
Figure 18.8
Program Control
110
17
MCR
RET
110
16 15
011
MCR
Master Control Reset
110
17
ZCL
110
16 15
011
Zone Control Last State
Common applications such as varying either packaged size or receipt
ingredient use these instructions. For example, packaging a product in two
different size of packages or converting a food product to a dietary food
product by changing its sugar content.
Before you program these two instructions, think about how you want
outputs to react when you change the process or operation.
Using the MCR instruction, rung logic shows:
If address 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 reset regardless of the state
of 110/16.
Using the ZCL instruction, rung logic shows:
If address 110/17 is false, then bit 011/15 is energized if 110/16 is set.
This is normal operation.
If address 11/17 is true, then bit 011/15 if left in its last state regardless
of the state 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