Serial Port Information
The following topics describe the RS-232, RS-422, and RS-485 standards and explain some of the issues involved with these types of serial communication.
The following table lists the features of the RS-232, RS-422, and RS-485 standards.
RS-232, RS-422, and RS-485 Features
| Feature | RS-232 | RS-422 | RS-485 |
|---|---|---|---|
| Type of transmission lines | Single ended | Differential | Differential |
| Maximum number of drivers | 1 | 1 | 32 |
| Maximum number of receivers | 1 | 10 | 32 |
| Maximum cable length | 50 ft | 4,000 ft | 4,000 ft |
| Maximum data rate | 20 kbytes/s | 10 Mbytes/s | 10 Mbytes/s |
| Maximum CMV | ± 25 V | ±7 V | +12 to –7 V |
| Driver output | 5 to 25 V | 2 to 6 V | 1.5 to 6 V |
| Driver load | <3 k | 100 | 60 |