Z-World Fox LP3500 User Manual - page 32

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Fox (LP3500)

3.4.1  RS-232

The LP3500 RS-232 serial communication is supported by an RS-232 transceiver. This trans-

ceiver provides the voltage output, slew rate, and input voltage immunity required to meet 

the RS-232 serial communication protocol. Basically, the chip translates the Rabbit 3000’s 

logic-level signals to RS-232 signal levels. Note that the polarity is reversed in an RS-232 

circuit so that a +2.8 V output becomes approximately -7 V and 0 V is output as +7 V. The 

RS-232 transceiver also provides the proper line loading for reliable communication.

RS-232 can be used effectively at the LP3500’s maximum baud rate for distances of up to 

15 m.

Logic-level signals are also possible on Serial Ports B, C, and E by changing the 0 

Ω

surface-mounted resistor jumper settings at locations JP1–JP6.

Serial Port E can be set to “listen” and “wake up” the LP3500 when the unit is in a low-

power mode.

3.4.2  RS-485

The LP3500 has one RS-485 serial channel, which is connected to Serial Port F on the 

Rabbit 3000 through an RS-485 transceiver. The half-duplex communication uses the 

Rabbit 3000’s PG0 pin to control the transmit enable on the communication line.

The LP3500 can be used in an RS-485 multidrop network. Connect the 485+ to 485+ and 

485– to 485– using single twisted-pair wires (nonstranded, tinned) as shown in Figure 13. 

Note that a common ground is recommended.