The RS232 and RS485 is an old serial interface. Both serial interfaces are the standard for data communication. This question is also very important and generally ask by an interviewer.
Some important difference between the RS232 and RS485
| Parameter |
RS232 |
RS485 |
| Line configuration |
Single –ended |
differential |
| Numbers of devices |
1 transmitter 1 receiver |
32 transmitters 32 receivers |
| Mode of operation |
Simplex or full duplex |
Simplex or half duplex |
| Maximum cable length |
50 feet |
4000 feet |
| Maximum data rate |
20 Kbits/s |
10 Mbits/s |
| signaling |
unbalanced |
balanced |
| Typical logic levels |
+-5 ~ +-15V |
+-1.5 ~ +-6V |
| Minimum receiver input impedance |
3 ~ 7 K-ohm |
12 K-ohm |
| Receiver sensitivity |
+-3V |
+-200mV |
