RS-422 查看數據表（PDF） - Unspecified

零件编号

产品描述 (功能)

生产厂家

RS-422

RS-422 AND RS-485 APPLICATION NOTE

Unspecified 

EIA Standard RS-485 Data Transmission

The RS-485 Standard permits a balanced transmission line to be shared

in a party line or multidrop mode. As many as 32 driver/receiver pairs can

share a multidrop network. Many characteristics of the drivers and receivers

are the same as RS-422. The range of the common mode voltage Vcm that

the driver and receiver can tolerate is expanded to +12 to -7 volts. Since the

driver can be disconnected or tristated from the line, it must withstand this

common mode voltage range while in the tristate condition. Some RS-422

drivers, even with tristate capability, will not withstand the full Vcm voltage

range of +12 to -7 volts.

Figure 1.6 shows a typical two-wire multidrop network. Note that the

transmission line is terminated on both ends of the line but not at drop points

in the middle of the line. Termination should only be used with high data

rates and long wiring runs. A detailed discussion of termination can be

found in Chapter 2 of this application note. The signal ground line is also

recommended in an RS-485 system to keep the common mode voltage that

the receiver must accept within the -7 to +12 volt range. Further discussion

of grounding can be found in Chapter 3 of this application note.

6

RS-422/485 Application Note

B&B Electronics -- PO Box 1040 -- Ottawa, IL 61350

PH (815) 433-5100 -- FAX (815) 434-7094

Share Link: