Rockwell Automation 1770-KF2 Data Highway or Highway Plus Interface Module User Manual - Manual (Page 101)

Message Packet Formats
Chapter 5
5-22
Unprotected Write
This command writes words of data into ay area of PC data table memory.
Use the SIZE field to specify the number of bytes to be read. To specify a
number of PC words, SIZE should be an even value because PC words are
two bytes long.
Command Format:
Reply Format:
TNS STS CMD
08
SRC DST
TNS STS CMD
48
SRC DST
ADDR DATA — Max of 242 Bytes
PLC Commands
PLC stations can execute all of the commands in the basic command set,
except the commands to set NAKs, ENQs, timeouts, and variables. They
can also execute the following commands, which apply only to PLC
controllers:
Disable Outputs
Enable Program
Enable Scan
Physical Read
Physical Write
The above are privileged commands. This means that only a computer
can initiate them. Their primary purpose is for uploading and
downloading PLC memory.