Vecow UMBC-1100 User Manual page 37

2.3.3 SW1~SW5 : Pull-up and Pull-down Bias Resistors
When an RS-422 and RS-485 network is in an idle state, all nodes are in listen
(receive) mode. Under this condition there are no active drivers on the network,
all drivers are tristated. Without anything driving the network, the state of the LINE
is UNKNOWN. If the voltage level at the RECEIVER's A and B inputs is less than
±200 mV the LOGIC level at the OUTPUT of the RECEIVERs will be the VALUE
1 19
of the last bit received. In order to maintain the proper idle voltage state, bias
RESISTORs must be applied to force the data LINEs to the idle condition.
4 1 4
JCOM1
JCOM2
JCOM3
JCOM4
JCOM5
©Vecow UMBC-1100 User Manual
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7
7
1
RS232
8
7
6
5
8
7
6
5
8
7
6
5
8
7
6
5
8
7
6
5
R1
R9 R9
4
R10 R2 R10
R2
L3 L4 L1 L2
L1 L3 L4
L2
R10
R11
7 1
2
8
1
4
2
SW1 SW2
1 7 1 7 1
7 7 1
2 8 2
1 1
1
1
1 2 8
7
10
10
1 1 10
1 10
1 7
RS422
4 8
3 7
2 6
1 5
4 8
3 7
2 6
1 5
4 8
3 7
2 6
1 5
4 8
3 7
2 6
1 5
4 8
3 7
2 6
1 5
GETTING TO KNOW YOUR UMBC-1100
R22
8 7
R23
R12 R24
1
1
SW3 SW4 SW5
2
30
8 8 2 8 2 8
2
1
1 1
1
7 7 7 7
1 10 1 10 1 10 1
4 1
RS485
4 8
3 7
2 6
1 5
4 8
3 7
2 6
1 5
4 8
3 7
2 6
1 5
4 8
3 7
2 6
1 5
4 8
3 7
2 6
1 5
4
24
12
11
4 1
4
3
2
1
4
3
2
1
4
3
2
1
4
3
2
1
4
3
2
1
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