849
Network Instructions Section 3-24
• Sending to a PLC operating as a Host Link Slave
When a CMND(490), SEND(090), or RECV(098) instruction is executed to
a serial port that supports the serial gateway function, the serial gateway
function can send any FINS command or send/receive data.
Communications from a Host Computer (Host Link)
It is possible to send FINS commands from a host computer to the PLC to
which it is connected as well as other devices in the network (CPU Units, Spe-
cial I/O Units, computers, etc.). In this case, the necessary Host Link header
and terminator must be attached to the FINS command when it is sent.
Communications Flags The operation of the communications flags is outlined below.
• The Communications Port Enabled Flag is reset to 0 when communica-
tions are in progress and set to 1 when communications are completed
(normally or not).
• The status of the Communications Port Error Flag is maintained until the
next time that data is transmitted or received.
• The Communications Port Error Flag will be reset to 0 the next time that
data is transmitted or received, even if there was an error in the previous
operation.
Serial cable
PLC
Host Link Slave
CMND
PLC
Host link FINS
Host computer
Host Link
FINS
command
Host Link header
Host Link FCS
and terminator
FINS command
0204
Busy
Communications Port
Enabled Flag
Network instruction
(SEND, RECV, or CMND)
Communications Port
Error Flag
Communications Port
Completion Code
Instruction 1
executing
Previous
completion
0000 (Normal
completion)
Instruction 2
executing
Instruction 3
executing
0000 (Normal completion)
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