Communication Guide
Standard connection
The standard connection conforms to the Modbus specifications, sepecially 2 wire multidrop serial bus diagram, presented at the website of Modbus.org in 2002 (Modbus_over_serial_line_V1.pdf, Nov.2002). Simple wiring diagram is like below.
The characteristics is like below in case of a direct connection to the bus.
Items | Contents | |
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Type of trunk cable | single, shielded, twisted pair cable. | |
Min 3rd cable | ||
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Maximum length of the bus | 1000m (3,2181 ft) (at 19.2kbps) | |
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Maximum number of | 32 stations (31 slaves) | |
stations without repeater | ||
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| �20m (66ft, at 1 tapoff) | |
Maximum length of tapoffs | �40m (131ft, divided by tapoff no. | |
| in | |
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| �450 - 650Ω Pullup resistor, 5V basis | |
| �450 - 650Ω Pulldown resistor, | |
Bus polarization | Recommend the polarization to Master at | |
| Common. There is no polarization at | |
| RS485 of EOCR . | |
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Line terminator | 120Ω Resistor, + /- 5% | |
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Common polarity | YES (connect 1 protection ground minimum | |
to the bus) | ||
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