How Fast can you Go?

Faster rise times will result in greater ringing amplitude. A higher value termination resistor will reduce the DC losses associated with extreme line lengths, allowing for much longer line lengths at the cost of ringing on the wires. The termination resistor has a significant impact on DC losses, so networks with long cable lengths may benefit from tweaking the termination resistor to a higher value. Should also be used on RS-485 networks if the driver is always enabled. This is not technically correct since RS-232 requires the use of voltages outside those of normal logic, but the input and output of an RS-232 driver look inverted on an oscilloscope, and most data sheets show the driver as an inverter. 200mV. This can cause a problem if the RS-485 network is using a UART to transmit data. This means that there can be 32 nodes capable to both transmit and receive.

This means the specification has a differential voltage requirement, and a common mode voltage requirement. Empirically determined means try it and see if it works. See the instructions on the converter you are using. See the section on polarity for more information. The third point C is discussed in the section on grounding. This installation should have a third wire connecting the earth ground/circuit common from the desktop PC to the laptop's RS-485 port circuit common. The driver must not exceed 10V differential, or 6V common mode (outputs relative to circuit common). Often RS-485 links are used for simple networks, and they may be connected in a 2 or 4 wire mode. This is exactly what is expected from the symbol of RS-485 figure 1, and exactly backwards from what is expected based on the signaling waveform of RS-485 figure 1, because this driver does not invert its input. RS-485 figure 2 shows a generator (driver) with two interface connection points labeled "A" and "B". RS-485 simply defines the interface connection points as "A" and "B" and shows the voltage relationship between "A" and "B" for the binary states of the two wires, not the binary state of the input to the driver.

7V. The receiver must recognize a differential voltage of greater than ±200mV as a binary value. 12V. The receiver must recognize a differential voltage of greater than ±200mV as a binary value. 200mV as a binary value, but different manufacturers can set the threshold where ever they want. Finally there is confusion from the IC manufacturers. Articles, application notes, even data sheets from semiconductor manufacturers discuss both the data rate and line length limits in RS-485. The RS485 standard is used when high speed serial data communications of 10 Mbps is needed. When the input is high the inverting output goes low, and when the input is low the inverting output goes high. For normal logic when the input of a driver is a 1 or high, the non-inverting output will go high. This problem can also be fixed by adding bias resistors to force the line to idle condition when a driver is not connected, but this has to be done on a network basis, not a device basis. Often, use of shielded CAT5/6 cable can give an adequate signal ground, although this is not recommended.

120 Ω cable should provide the best performance, but the 100 Ω CAT-X cable may you have laying around may also work. You may not have the polarity you expect. The annex of RS-485 states that "When employed, the shield shall be connected only to frame ground at either or both ends depending on the specific application." Shields usually have a lot more copper (and/or aluminum) than a single wire and can therefore carry a lot more current. How fast can you go? This can be extended further by using "automatic" repeaters and high-impedance drivers / receivers. RS-485, also known as TIA-485(-A) or EIA-485, is a standard, originally introduced in 1983, defining the electrical characteristics of drivers and receivers for use in serial communications systems. I've been told that 10BASE-T Ethernet and SCSI cables use a bunch of RS-485 pairs -- is that right ? This applies to the 8 bit version of the original 50 way SCSI interface. If they don't communicate, reducing the bit rate may make the two devices function together. If the can't, try reducing the bit rate. If you are pushing the data rate above 100kbit or the line length above 1000 meters, you may want to use a better grade of wire.