The maximum cable length depends on the baud rate and the type of cable used. As a general rule, the maximum cable length is around 100 meters at 9600 bps, 50 meters at 19200 bps, and 20 meters at 38400 bps. However, it's recommended to consult the RS-485 standard and perform signal integrity analysis to determine the maximum cable length for a specific application.
To prevent signal reflections, a termination resistor (typically 120 ohms) should be placed at both ends of the RS-485 bus. The termination resistor should be connected between the differential signal lines (A and B) and should be matched to the characteristic impedance of the cable.
Yes, the SN65HVD21P can be used in a multi-point configuration. However, it's essential to ensure that only one device is transmitting at a time to prevent data corruption. A master-slave architecture or a token-passing protocol can be used to manage the transmission and reception of data in a multi-point configuration.
The maximum number of devices that can be connected to the RS-485 bus depends on the bus loading and the type of devices used. As a general rule, up to 32 devices can be connected to the bus, but this number can be limited by the bus loading and the device's input impedance.
Hot-swapping of devices on the RS-485 bus can cause signal disturbances and data corruption. To handle hot-swapping, it's recommended to use a bus repeater or a hub to isolate the devices and prevent signal reflections. Additionally, a fault-tolerant protocol can be used to detect and recover from errors caused by hot-swapping.
SN65HVD21P datasheet
by Texas Instruments
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