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Chapter 12
Application Fields
Figure 12.1 shows the station management message packet format
including the application fields. The application fields are those station
management message fields defined at the application layer. The
application fields you use in a station management message will vary
depending on the message you send. We describe all of the fields here.
Here is an example showing the format of application fields:
All values we show in the fields are hexadecimal unless otherwise stated.
CMD (Command) — This one-byte field specifies the type of message.
Here are the types of messages and their associated CMD values:
Message Type
CMD Value (Hex)
DATA SIZE+1 — This one-byte field is only in the read values
command. It specifies the number of bytes of data in the reply, plus one.
The additional one allows for the one-byte field that precedes the data
field in the reply.
PID (Parameter ID) — This variable-length field specifies the channel
affected and the type of parameter you want to examine and/or change. It
is preceded by a one-byte SIZ field. All parameter IDs are one byte long,
so the value in the SIZ field must be 01 hex. The Parameter ID column
in Table 12.A tells you which PID value to use based on the type of
command you are sending. For parameters of the 1779-KFL link to its
host, the most-significant hex digit indicates the channel affected (1 or 2);
the least-significant digit specifies the type of parameter.
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Troubleshooting
