表 2.2. RS232,RS422,RS423,RS485之间的对比
| |
RS232 |
RS422 |
RS423 |
RS485 |
| Differential |
no |
yes |
no |
yes |
| Max number of drivers |
1 |
1 |
1 |
32 |
| Max number of receivers |
1 |
10 |
10 |
32 |
| Modes of operation |
half duplex, full duplex |
half duplex |
half duplex |
half duplex |
| Network topology |
point-to-point |
multidrop |
multidrop |
multidrop |
| Max distance (acc. standard) |
15 m |
1200 m |
1200 m |
1200 m |
| Max speed at 12 m |
20 kbs |
10 Mbs |
100 kbs |
35 Mbs |
| Max speed at 1200 m |
(1 kbs) |
100 kbs |
1 kbs |
100 kbs |
| Max slew rate |
30 V/μs |
n/a |
adjustable |
n/a |
| Receiver input resistance |
3~7 kΩ |
≧ 4 kΩ |
≧ 4 kΩ |
≧ 12 kΩ |
| Driver load impedance |
3~7 kΩ |
100 Ω |
≧ 450 Ω |
54 Ω |
| Receiver input sensitivity |
±3 V |
±200 mV |
±200 mV |
±200 mV |
| Receiver input range |
±15 V |
±10 V |
±12 V |
–7~12 V |
| Max driver output voltage |
±25 V |
±6 V |
±6 V |
–7~12 V |
| Min driver output voltage (with load) |
±5 V |
±2.0 V |
±3.6 V |
±1.5 V |
