Rockwell Automation 2706-MB1 MESSAGEVIEW 421 SOFTWARE MANUAL - Manual (Page 110)

5–21 Communications Overview
Publication 2706-817
Example: Block Transfer Write
In this example, the MessageView 421 terminal is assigned to rack
#3 and its starting module group is 0. A Numeric Variable Display
variable has the address N7:0, and its value is written by the logic
controller to a portion of the data block being transferred.
BTW
(EN) BLOCK TRANSFER WRITE
Rack 03
Group 0
Module 0
Control Block N16:1
Data File N7:0
Length 10
Continuous N
➀ The PLC receives and stores data from
an input device, in this example a flow
sensor.
➁ The PLC ladder logic program initiates a
block transfer of a data block (10 words)
containing the display data.
Display variable with
Tag Name “Flow_Rate” from
Address N7:5
➂ The MessageView terminal receives the data and
determines the starting address where the data is
written by matching the block size with the address
entered in the Communication Setup utility.
➄ The MessageView updates the Numeric Variable
Display using the data from the controller.
Flow Rate
Transducer
Data From
PLC
N7:5
10 WORDS
N7:0
N7:1
N7:2
N7:3
N7:4
N7:5
N7:6
N7:7
N7:8
N7:9
Flow Rate Data
➃ The MessageView now carries a copy of that
segment of the logic controllers data table.
Tag Name = Flow_Rate