Rockwell Automation SMC Dialog Plus, User Manual

Page: 132 / 189

Serial Communications 8-23
Example #3 Ladder Logic Program
Machine
START
Push Button
: 016
SMC
START
Command
: 021
11 01
Machine
STOP
Push Button
: 016
SMC
OPTION
Command
: 021
First Rung: When the Machine START push button is pressed, the PLC sends a START command to the SMC Dialog Plus controller. The SMC Dialog
Plus controller will start if no STOP command is being issued by the PLC or any other control device. (The start button is a normally open contact in this
example.)
02 01
02
Second Rung: When the Machine STOP push button is pressed, the PLC sends an OPTION command (“pump stop" in this example) to the SMC
Dialog Plus controller. (The stop button is a normally closed contact in this example.) The branch provides a logic “latched" circuit which exerts the
OPTION command until the feedback from the SMC Dialog Plus controller indicates that it has returned to a “stopped" status (not running).
SMC
OPTION
Command
: 021
SMC
Running
Bit
: 021
12
Third Rung: The SMC Fault Bit initiates a PLC block transfer write to the communication module, requesting a parameter value read (SMC Dialog Plus
controller Parameter 19, Fault Buffer #1, in this example).
SMC
Fault
Bit
: 021
07
BT
Read
Available
BTR_AVAIL BT
Write
Available
BTW_AVAIL
: 020 : 020
12 15
BT
Error
BT_ERROR
14
BLOCK TRNSFR WRITE
Rack:
Group:
Module:
Control Block:
Data File:
Length:
Continuous:
BTW
02
0
0
BT11:0
N10:10
3
N
(EN)
(DN)
(ER)
Fourth Rung: A block transfer read occurs whenever the communication module's BT Read Available status bit is true, in this example, the
communication module responds to the PLC request (BTW in the third rung) by supplying the value stored in Parameter 19.
: 020
12
BT
Read
Available
BTR_AVAIL
BLOCK TRNSFR READ
Rack:
Group:
Module:
Control Block:
Data File:
Length:
Continuous:
BTR
02
0
0
BT11:1
N10:90
4
N
(EN)
(DN)
(ER)
: 020