2.4. RS232和RS485、RS422之间的对比 -

2.4. RS232和RS485、RS422之间的对比

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


2.3. RS232和TTL的对比		2.5. RS232和SPI、I2C的对比