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MAP450D

2.3. RS-422/485 (Network mode)

Network mode supports the 3-wire and 5-wire RS-422/485 configurations. The 3-wire configuration has both transmit and receive on the same pair of wires plus a signal common. The 5-wire configuration has differential signal pairs for transmit and receive plus a signal common. In both configurations the signal pairs must be twisted and surrounded by an overall shield.

OIT

 

TB1

 

 

1

Shield

 

 

+24V

2

 

* COM

3

 

RXD+

4

 

RXD-

5

 

TXD+

6

 

TXD-

7

 

* RTN

8

 

*RTN and COM are internally connected in OIT.

Power Supply

+24V

GND

From or To

Host or OIT

CHASSIS GND

RXD+/TXD+

RXD-/TXD-

SIG GND

SIG GND

Figure 5 3-Wire RS-422/485 (Network mode)

NOTE: When using 3-wire RS-422/485, Jumper JP4 must be in position “B”. Refer to section 2.4 for instructions.

OIT

 

TB1

 

 

1

Shield

 

 

+24V

2

 

* COM

3

 

RXD+

4

 

RXD-

5

 

TXD+

6

 

TXD-

7

 

* RTN

8

 

*RTN and COM are internally connected in OIT.

Power Supply

+24V

GND

From or To

Host or OIT

CHASSIS GND

TXD+

TXD-

RXD+

RXD-

SIG GND

SIG GND

Figure 6 5-Wire RS-422/485 (Network mode)

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 same time. 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-wire RS-422/485 may increase development time.

1010-0046A, REV 00

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B&B Electronics MAP450D installation manual RS-422/485 Network mode, Oit