Kontron PCI-COM-8ULP, Руководство пользователя

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PCI-COM-8ULP User’s Guide page 21
Option Selection
To help you locate the jumpers described in this section, refer to the Option Selection
Map at the end of this section. Operation of the serial communications section is
determined by jumper installation as described in the following paragraphs.
For the convenience of the user, instructions for the placement of the jumpers is also
silk screened on the back of the card.
Terminations
A transmission line should be terminated at the receiving end in its characteristic
impedance. Installing a jumper at the locations labeled LDxO applies a 120
Ω load
across the transmit/receive input/output for RS485 operation.
Jumpers having to do with the termination of each channel are located near the output
connector. They are labeled by channel. The load jumper is labeled “LD”. The other two
jumpers are used to connect the transmit and receive lines for the two wire RS485
mode.
120
0.01 F
Tx+/R x+
Tx-/R x-
LD
µ
Figure 1: Simplified Termination Schematic
In RS485 operations where there are multiple terminals, only the RS485 ports at each
end of the network should have terminating impedance as described above. To so
terminate the COM A port, place a jumper at the location labeled Ch A -LD. To
terminate the COM B, COM C, COM D, COM E, COM F and COM H ports, place
jumpers at locations labeled Ch B - LD, Ch C - LD, Ch D - LD, Ch E - LD, Ch F - LD, Ch
G - LD and Ch H - LD respectively.
Also, for RS485 operation, there must be a bias on the TRX+ and TRX- lines. If the
LPCI-COM-8SM card is not to provide that bias, contact the factory technical support.