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Data Highway Message Set
Chapter 8
821
Unprotected Write Block
Use this command to write a block of data into any contiguous area of the
data table in a programmable controller. Use the address (L ADDR) field
to specify the logical byte address of where to start to write this block of
data.
Command Format:
SuccessReply Format:
TNS
2 Bytes
CMD
08
USER
NODE
LINK
STS
00
TNS
2 Bytes
CMD
48
USER
NODE
LINK
STS
00
L ADDR
2 Bytes
DATA
242 Bytes Max.
Unless otherwise stated, values shown are in hexadecimal, and each block
shown represents one byte.
In “Application Fields,” we described the Data Highway message fields
defined at the application layer. Here, we describe the format of each
specific type of PLC-2 command message and success-reply message at
the application layer. In each of these formats, we also show the Data
Highway fields to indicate where the application-layer fields fit in the
message packet. PLC-2 stations can execute all of the basic commands.
They can also execute the following commands, which apply only to
PLC-2 family controllers:
Enter Download Mode
Enter Upload Mode
Exit Download/Upload Mode
Physical Read
Physical Write
Set Data Table Size
The above commands are privileged commands. This means that only a
computer can initiate them. Their primary use is for uploading and
downloading PLC-2 memory.
PLC2 Message Formats