9.2.1.1 Data Rate and Bus Length

There is an inverse relationship between data rate and cable length, which means the higher the data rate, the short the cable length; and conversely, the lower the data rate, the longer the cable length. While most RS-485 systems use data rates between 10 kbps and 100 kbps, some applications require data rates up to 250 kbps at distances of 4000 feet and longer. Longer distances are possible by allowing for small signal jitter of up to 5 or 10%.

Figure 21. Cable Length vs Data Rate Characteristic

Even higher data rates are achievable (that is, 20 Mbps for the THVD1428) in cases where the interconnect is short enough (or has suitably low attenuation at signal frequencies) to not degrade the data.