Allen-Bradley 1779-KFMR User Manual page 161

Chapter 10
PWD (Password) — This four-bit sub-field specifies the code that
must be used if the remote command is stored with one of the other
protection sub-fields set to restrict access to anyone with the password.
The password sub-field is in each RC control command. The complete
remote command protection field is only in the store RC command and
the read RC reply packet.
SIZE — This two-byte field specifies the number of bytes in the remote
command. This field is only in the store RC command and in the read RC
reply.
Remote Command Fields (Application Layer)
Figure 10.1 shows the format of the RC control message packet including
the remote command fields at the application layer. The remote command
fields are the fields defined at the application layer that make up the
remote command. The remote command is a command within a
command. The remote command is sent to the destination remote station
to be stored and then initiated by that remote station. The remote
command fields are only in the store RC command, store/initiate/delete
RC command, and read RC reply packets. Here we describe these remote
command fields:
SEL (Select) — This one-byte field specifies the message set for the
remote command. You can select either the Data Highway message set or
the time-critical message set with the following select-field hexadecimal
values:
00 — Data Highway Message Set
01 — Time-Critical Message Set
CMD (Command) — This one-byte field specifies the type of action to
be performed by the command executor at the station which is the
ultimate destination of this remote command when it is initiated by the
remote station where it is stored. The possible command-field
hexadecimal values are:
1F — Read Block
20 — Write Block