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Chapter 8
PLC 3 Message Packets
Timeout
A two-minute timer will start when the 1779-KP2 interface receives an
enter upload mode command or an enter download mode command. The
timer will restart each time a command in the upload or download
procedure is received. If the timer times out, the interface exits the mode
as if an exit download/upload command were received.
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-3 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-3 stations can execute all of the basic commands.
They can also execute the following commands, which apply only to
PLC-3 family controllers:
Non-Privileged Commands
Write Bit
Read File
Write File
Read Block
Write Block
Privileged Commands
Download Privilege
Upload Privilege
Shutdown
Physical Write
Physical Read
Restart
Only a computer or another PLC-3 controller can initiate the
non-privileged PLC-3 commands listed above. The primary function of
these commands is to transfer data between PLC-3 files. These files may
be in the same PLC-3 controller or in two different PLC-3 controllers.
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Troubleshooting
