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9-2.
RS-485 connection
■Two-wire type (point to point)
PLC/Host like a PLC,
programmable display, etc.
(Master)
- Use a twisted pair cable for connection. (Noise margin is improved.)
However, a parallel two-core cable is enough for short-distance connection.
- Install terminating resistance each on the host side and F701-P side.
- The SG terminal is a ground terminal used in circuits (to protect the circuits).
If the F701-P body and the equipment on the other end of the connection are class-D-grounded,
usually there is no need to use the SG terminal.
However, if there is a need to connect it according to the on-site situation, connect it after
checking the specifications of the equipment on the other end.
Attention
■Two-wire type (multi point)
Host
A
B
Terminating resistance
55
Terminating resistance
(accessory)
Terminating resistance
A
B
A
B
On some master equipment, A and B may be expressed in reverse.
If communication fails, interchange A and B.
F701-P
A
B
Twisted pair cable
F701-P
A
B
A
B
(Slave)
F701-P
F701-P
A
B
A
B
9 RS-485 INTERFACE
* Logic
- Mark state (OFF)
V
-V
<-0.2V
A
B
- Space state (ON)
V
-V
>0.2V
A
B
V
: A terminal voltage
A
V
: B terminal voltage
B
F701-P
A
B
Terminating
resistance
55
Chapter
9
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