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ELECTRICAL INSTALLATION
2.4
Pull-up and Pull-down Resistors – Figs. 2.1 and 2.2
To prevent false triggering of slaves when the master (host computer) is inactive,
pull-up and pull-down resistors must be fitted to the RS422/485 interface in the host
computer – see Figs. 2.1 and 2.2.
+5V
0V
1.8k
Ω
Pull-up
Resistor
1.8k
Ω
Pull-down
Resistor
Host Computer
Rx–
Rx+
Tx–
Tx+
'A'
'A
'B'
'B
GND
20
21
22
23
24
Tx+/Rx+
Tx–/Rx–
GND
+5V
0V
1.8k
Ω
Pull-up
Resistor
1.8k
Ω
Pull-down
Resistor
Host Computer
Rx–
Rx+
Tx–
Tx+
'A'
'A
'B'
'B
GND
Tx+/Rx+
Tx–/Rx–
GND
11 12 13
Fig. 2.1b Two-wire Operation – L160
Fig. 2.1a Two-wire Operation – L150
Summary of Contents for DATUM L150
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