8
Protocol Overview Section 1-3
2. A 1:1 NT Link is not supported.
3. No-protocol mode can be used with CS/CJ-series CPU Units with Unit Ver.
3.0 or later only.
A connection example for each serial communications mode is shown in the
following sections for a Serial Communications Unit. The examples apply
equally as well to the Serial Communications Boards.
1-3-1 Host Link Mode
In Host Link mode, C-mode commands (Host Link commands) or FINS com-
mands can be sent from a host computer to read or write I/O memory in the
PLC or to control the PLC’s operating modes. The host computer can be a
personal computer or a Programmable Terminal. The FINS commands are
sent with other data, such a Host Link header and terminator.
In Host Link mode, SEND(090), RECV(098), and CMND(490) instructions can
be used to send FINS commands from PLC to the host computer to read
data, write data, or perform other operations. This is called slave-initiated
communications or unsolicited communications. The FINS commands are
sent with other data, such a Host Link header and terminator.
Note 1. FINS commands can be sent across up to three different networks (count-
ing the local network) to a PLC on a remote network or to a host computer
connected to a PLC on a remote network.
2. Programming Devices can also be connected in Host Link mode.
Sending C-mode Commands
Sending FINS Commands
Host Link
C-mode (Host Link)
command
FINS
command
Host Link
Host Link
header
Host Link
terminator
FINS commands can also be sent to
PLCs on remote networks.
FINS
command
Host Link
Host Link
header
Host Link
terminator
FINS command
Remote network
(Controller Link or
Ethernet)
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