Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 403)

Publication AG-UM008C-EN-P - February 2005
Sample Ladder Logic E-21
Logix DF1 Half-Duplex Slave Report-By-Exception MSG
Logix5550 DF1 Half-Duplex Slave "Report-By-Exception" MSG Logic
Copy all of the "live" discrete and analog values to be written as a "report-by-exception" MSG to the Master into a data compare array. This copying occurs
continuously between successful MSG writes. If multiple changes occur after the MSG begins executing, and before the MSG has s
last change will be recorded and sent during the next MSG execution. Care should be exercised with constantly changing analog data so that the MSG doesn’t
continuously retrigger, thus negating the efficiencies of a "report-by-exception" scheme. In this example, the Logix5550 array "Data_buffer" will be sent immediately
upon any change or every 15 seconds, whichever occurs first.
0
message1.DN
Copy File
Source Data_buffer[0]
Dest Data_compare[0]
Length 6
COP
EN
DN
Timer On Delay
Timer timer1
Preset 15000
Accum 0
TON
Logix5550 DF1 Half-Duplex Slave "Report-By-Exception" MSG Logic
continuously between successful MSG writes. If multiple changes occur after the MSG begins executing, and before the MSG has successfully completed, only
continuously retrigger, thus negating the efficiencies of a "report-by-exception" scheme. In this example, the Logix5550 array
upon any change or every 15 seconds, whichever occurs first.
If 15 seconds have elapsed since the last successful completion of the MSG write, snapshot the current data values for writing to the Master and retrigger the
1
timer1.DN
Copy File
Source Data_compare[0]
Dest Data_write[0]
Length 6
COP
U
message1.EN
JMP
label_1
If 15 seconds have elapsed since the last successful completion of the MSG write, snapshot the current data values for writing
MSG (regardless of whether data values have changed since the last write). (regardless of whether data values have changed since the last write).
If the MSG is enabled, skip over the data comparison rungs directly to the MSG rung. If the MSG has just completed in error, r etrigger the MSG immediately and
jump directly to the MSG rung.
2 /
message1.DN message1.ER
U
message1.EN
JMP
label_1
If the MSG is enabled, skip over the data comparison rungs directly to the MSG rung. If the MSG has just completed in error, r
jump directly to the MSG rung.
Data array comparison rung.
3 RES
control1
control1.IN
U
control1.IN
EN
DN
ER
File Search/Compare
Control control1
Length 6
Position 5
Mode ALL
Expression (Data_compare[control1.pos]<>Data_write[control1.pos])
FSC
Data array comparison rung.
ch will write Data_write to the Master).
4
control1.FD
Copy File
Source Data_compare[0]
Dest Data_write[0]
Length 6
COP
U
message1.EN
If values differ between the Data_compare and Data_write arrays, copy Data_compare into Data_write, and trigger the MSG (whi
"Report-by-exception" write instruction to the Master. This MSG block is configured to write "Data_write" out the serial port to the Master (path 2,0), using a PLC5
Typed Write.
5 LBL
label_1
EN
DN
ER
Type - PLC5 Typed Write
Message Control message1 ...
MSG
"Report-by-exception" write instruction to the Master. This MSG block is configured to write "Data_write" out the serial port
Typed Write.
(End)