B&B Electronics MAP450D installation manual Network Termination

12 MAP450D

Network Termination

The com-link cable must be properly terminated to reduce the amount of interference and noise pickup from the surrounding environment. This is accomplished by using a termination circuit at both ends of the network cable. The following figure shows a typical termination circuit. The host termination is only needed if the host controller’s RS-422/485 adapter does not contain any built-in terminator circuitry. The end termination must be done at the extreme end of the com-link cable.

HOST

TERMINATOR TERMINATOR

OIT3600 MAP460D OIT3160

HOST TERMINATION

Vcc
Tx+
Tx-
	470 Ohm
	to
Rx+	10 KOhm
	120 Ohm
	to
Rx-	240 Ohm
	470 Ohm
	to
SIGNAL GND	10 KOhm
CHASSIS GND
	EARTH
	GROUND

FROM HOST +

FROM HOST -

TO HOST +

TO HOST -

SIGNAL GND SHIELD

END TERMINATION

120Ohm

to

240Ohm

DO NOT

CONNECT

Network Grounding

To communicate properly, serious attention must be paid to the grounding scheme of the devices connected to the com-link. Improper grounding, improper termination, and faulty shielding of the com-link are the most common causes of system failure in a multidrop network.

	Shield
Signal Ground	Signal Ground
From Host +	From Host
From Host -
To Host +	To Host
To Host -
Shield
To OIT	To OIT

1010-0046A, REV 00