I-o-display-systems Basic I/O Product Manuel d'utilisateur télécharger pdf (Page 61)

Installation 2

2-7(Vol.2)

Network load V.S. Noise suppression:

In order to improve RS-485 Bus noise immunity, particularly under tri-state conditions, a pair

of “Network Bias Resistors” have been installed in each BASIC I/O AD unit. This design

feature has been implemented in order to satisfy the majority of our customers. If it is

necessary to multidrop more than eight BASIC I/O AD units(but ultimately less than thirty-

two devices), It will be necessary to remove these network bias resistors so as to not exceed

the maximum bus loading. However, in order to retain noise immunity, the network bias

resistors should remain installed in at least one BASIC I/O AD on the network. Figure 2-4

below shows the location of the four network bias resistors.

R34 is the 1.5k from prior +bias resistor

R35 is the 1.5k from prior - bias resistor

R36 is the 1.5k from next + bias resistor

R37 is the 1.5k from next - bias resistor

Figure 2-2 Network Bias resistor locations

1 2 ... 56 57 58 59 60 61 62 63 64 65 66 ... 80 81

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I-o-display-systems Basic I/O Product Manuel d'utilisateur Page 61