Understanding Data Storage; Example Plc Block Transfers - Allen-Bradley 1203 Series User Manual

Understanding Data Storage

Example PLC Block Transfers

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In order to use the block transfer instructions in the ladder program, it
is necessary to reserve several words for data storage. Some of these
words are required for internal use by the block transfer function, and
some contain the block transfer message information. Refer to
Appendix B for detailed information on the required data in data files
for different block transfer messages.
Figure 5.3 and Figure 5.4 are examples of block transfer
programming from PLC controllers to a Remote I/O communications
module. The BTW_AVAIL and BTR_AVAIL bits from the module
status word (I:010 in these examples) are used in these examples. The
examples also show how user logic can be used to enable or disable
the block transfer operations.
Figure 5.3
This rung performs a Block Transfer Write to the 1203-GD1 at Rack Address 1, Starting Group 0
(the Module number is always 0 with these adapters). The data instructs the adapter to send a SCANport message.
When this message has completed, the response can be read with a BTR.
User BTW BTR
Logic Available Available
B3:0 I:010 I:010
0 15 12
This rung performs a Block Transfer Read from the 1203-GD1 at Rack Address 1, Starting Group 0
(the Module number is always 0 with these adapters). The response contains the data read from the SCANport
Product (as instructed by the previous BTW).
BTR
Available
I:010
12
Using Block Transfer Messages
Example for a PLC-5/15 or PLC-5/25
BTW BTW
Block Transfer Write
Module Type Generic Block Transfer
Rack
Group
Module
Control Block
Data File
Length
Continuous
BTR BTR
Block Transfer Read
Module Type Generic Block Transfer
Rack
Group
Module
Control Block
Data File
Length
Continuous
5–3
EN
001 DN
0
0 ER
N11:0
N12:0
64
No
EN
001 DN
0
0 ER
N11:5
N12:70
64
No
END