Rockwell Automation 2706-MB1 MESSAGEVIEW 421 SOFTWARE MANUAL - Manual (Page 111)

5–22 Communications Overview
Publication 2706-817
Example: Transferring Multiple Blocks
Multiple block transfers use a single channel (single Module Control
and Status Bytes defined). Each block transfer read or block transfer
write must be a unique length since the MessageView terminal uses
the block size to determine the starting location of the read or write.
The following is an example of a block transfer write of two blocks.
BTW
(EN) BLOCK TRANSFER WRITE
Rack 03
Group 0
Module 0
Control Bloc N16:6
Data File N90:10
Length 60
Continuous N
➀ The PLC ladder logic program initiates
multiple block transfers of 2 data blocks
(7 words and 60 words).
➁ The MessageView terminal receives the first data
block and determines the starting address N7:0
where the data is written by matching the block size
with the address entered in the Communication Setup
utility.
The MessageView handles the second block in the
same manner.
Data From
PLC
N7:0
N7:1
N7:2
N7:3
N7:4
N7:5
N7:6
N7:7
N7:8
N7:9
➂ The MessageView carries a copy of the
logic controller data tables N7:0 to N7:6.
BTW
(EN) BLOCK TRANSFER WRITE
Rack 03
Group 0
Module 0
Control Block N16:1
Data File N7:0
Length 7
Continuous N
Data From
PLC
➄ The MessageView display variables are updated
using the new data.
Block 1 Transfer N90:8
N90:9
N90:10
N90:11
➃ The MessageView carries a copy of the
logic controller data tables N90:10 to N90:69.
Block 2 Transfer
. . .
N90:12
N90:67
N90:68
N90:69
N90:70
N90:71
Note: If interfacing to an Allen-Bradley PLC2, single block transfer
is recommended.