The RS-485 standard has typical curves similar to those shown in Figure 11-4. These curves show the inverse relationship between signaling rate and cable length. If the data rate of the payload between two nodes is lower, the cable length between the nodes can be longer. Use below Figure as a guideline for cable selection, data rate, cable length and subsequent jitter budgeting.

Figure 11-4 Cable length vs Data rate characteristics

The current supplied by the driver must supply into a load because the output of the driver depends on this current. Add transceivers to the bus to increase the total bus loading. The RS-485 standard specifies a hypothetical term of a unit load (UL) to estimate the maximum number of possible bus loads. The UL represents a load impedance of approximately 12 kΩ. Standard-compliant drivers must be able to drive 32 of these ULs. The ISOW14x2 devices have 1/8 UL impedance transceiver and can connect up to 256 nodes to the bus.