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5–13
Note from the figure that three octal digits are available: Octal Digit 0,
Octal Digit 1, and Octal Digit 2.
Use Octal Digits 1 and 2 to set the 1785-KE’s Data Highway Plus address
from 00-77. These digits also set the lower two digits of the 1785-KE’s
address on the multidrop network.
Octal Digit 0 is an multidrop address expansion digit. It sets the most
significant (highest) digit of the 1785-KE multidrop address. If your
multidrop network only requires addresses 000-077 octal, you can set this
digit to 00 (switch position DOWN DOWN). If you need to use addresses
higher than 000-077 you will need to set this digit to 1 2 or 3.
See Using
the Multidrop Address Expansion Digit
later in this chapter for more
information on setting this digit.
In this example, we send a message from the master (1771-KGM/PLC-2)
at multidrop address 014 (octal), through the 1785-KE at address 021
(octal), to the PLC-5 with Data Highway Plus address 011 (octal).
The master sends the message to the PLC-5 address 011 (octal). The
1785-KE recognizes the address as one of the addresses on the Data
Highway Plus link and passes the message through to address 011. The
PLC-5 executes the command, processes a reply to the master, and returns
the reply to the 1785-KE. Later, when the master polls for address 011, the
1785-KE returns the response from address 011.
In this communication, the 1785-KE is transparent to the master. The
master is polling and sending messages only to the PLC-5 at address 011.
The following example shows the PLC-2 program to send a command
from the PLC-2/1771-KGM master at address 014 (octal), through the
1785-KE, to the PLC-5 at Data Highway Plus address 011 (octal).
Important:
Since the PLC-5 is communicating with a PLC-2, the PLC-5
must have a file set up to look like a PLC-2 data table. The PLC-5 file
must be the decimal equivalent of the PLC-2/1771-KGM node address.
Since the PLC-2/1771-KGM is at address 014 (octal), the PLC-5 must
create file 012 (014
8
= 012
10
)to communicate with the PLC-2.
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