2.3. RS-422/485 (Network mode)Network mode supports the 3-wire and 5-wire RS-422/485 configurations. The
3-wireconfiguration has both transmit and receive on the same pair of wires plus a
signalcommon. The 5-wire configuration has differential signal pairs for transmit
andreceive plus a signal common. In both configurations the signal pairs must be
twistedand surrounded by an overall shield.
NOTE: When using 3-wire RS-422/485, Jumper JP4 must be in position “B”.
Referto section 2.4 for instructions.
5-wire RS-422/485 supports full-duplex communications; which means that the
host controller can trasmit data to the OITs and receive data from the OITs at the
sametime. 3-wire RS-422/485 only supports half-duplex communications; which
means that the host controller cannot transmit and receive data at the same time.
Although 3-wire RS-422/485 installations may be less costly than 5-wire
installations, the increased complexity in programming the host controller for
3-wireRS-422/485 may increase development time.
10 MAP450D
1010-0046A,REV 00
5
COM
RXD+
RXD-
+24V
3
4
2
1
TB1 Shield
OIT
Fromor To
Hostor OIT
+24V
GND
PowerSupply
RTN 8
*
*
RTNand COM are internall
y
connectedin OIT.*
7
TXD+
TXD-
6
CHASSISGND
RXD+/TXD+
RXD-/TXD-
SIGGND
SIGGND
Figure5 3-WireRS-422/485 (Network mode)
5
COM
RXD+
RXD-
+24V
3
4
2
1
TB1 Shield
OIT
Fromor To
Hostor OIT
+24V
GND
PowerSupply
RTN 8
*
*
RTNand COM are internall
y
connectedin OIT.*
7
TXD+
TXD-
6
CHASSISGND
TXD+
TXD-
RXD-
SIGGND
RXD+
SIGGND