Specifications

Chapter 4 Wiring 23
RS-485 signal wiring
The RS-485 standard supports half-duplex communication. This
means that just two wires are needed to both transmit and receive
data. Handshaking signals (such as RTS, Request To Send) are
normally used to control the direction of the data flow and to switch
the transmission accordingly. In RS-485 mode, the PCL-846 automat-
ically senses the direction of the data flow and switches the transmis-
sion direction — no handshaking is necessary. This means a user can
build an RS-485 network with just two wires. This RS-485 control is
completely transparent to the user. The Software written for half
duplex RS-232 works without the need for any modification.
RS-485 wiring topology
Wiring connections are as follows:
PCL-846 DTE (male DB-9) Terminal DTE
Pin Signal Signal
2DATA+ DATA +
1DATA- DATA -