SG-785 Hardware User Guide
Ver. 1.0
Last Modified 10/26/2009
Introduction
The SG-785 is an optional module that is used to improve the communication
of RS-485 network. It provides switch selectable pull-high and pull-low
resistors on RS-485 network. It also has 15-step switch selectable termination
resistor such that the user can select a proper termination resistor to be
connected to the RS-485 network easily.
Specifications
General
Interface RS-485
Pull-high/pull-low Resistance 1k Ω
Termination Resistance 15 steps, 65 ~ 560 Ω
LED Display
1 red LED as power indicator
1 green LED as termination indicator
Power
Input Range 10 ~ 30 VDC
Power Consumption 0.5W, 24 VDC
Environment
Operating Temperature -25 °C ~ +75 °C
Storage Temperature
-40 °C ~ +80 °C
Humidity 5 ~ 95 % RH, non-condensing
SG-785 Pin Assignment
LED Display
PWR Power LED, Red
TR Termination Resistor LED, Green
Switches
TR Termination Resistor Setting
SW Termination Resistance and Pull-high/Pull-low Setting
Terminal Block
(Y)DATA+, (G)DATA- RS-485 Data Line
(R)+Vs, (B)GND Power Line
F. G. Frame Ground
SG-785 Switch Setting
RS-485 Termination Resistance Setting
SW1 SW2 SW3 SW4 Termination Resistance (ohm)
ON ON ON ON 65
ON ON ON OFF 74
ON ON OFF ON 76
ON OFF ON ON 81
ON OFF OFF ON 99
ON OFF ON OFF 96
ON ON OFF OFF 88
ON OFF OFF OFF 120
OFF ON ON ON 144
OFF ON ON OFF 193
OFF ON OFF ON 207
OFF ON OFF OFF 330
OFF OFF ON ON 256
OFF OFF ON OFF 470
OFF OFF OFF ON 560
RS-485 pull-high and pull-low setting
SW5 SW6 RS-485 Data Line Status
OFF OFF No pull-high/pull-low to RS-485 data line
ON OFF Add a pull high resistor to DATA+ line
OFF ON Add a pull low resistor to DATA- line
ON ON
Add a pull high resistor to DATA+ line and add a pull
low resistor to DATA- line
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