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thunks » QBasicFAQ » Calculating and Validating NMEA Checksums » CppBuilder » CMOS_C » The GPRMC Sentence » TurboCpp » BeginnersGuideToCurl » Curl Content Language » QbasicFAQ_Mouse » rs 485
RS-485
The RS-485 standard was developed jointly by two trade associations: the Electronic Industries Association ( ?EIA) and the Telecommunications Industry Association (TIA). The EIA once labeled all its standards with the prefix "RS" (Recommended Standard). Today, various extensions of the RS-485 standard accommodate a large variety of applications. The RS-485 and RS-422 standards have much in common, and are often confused for that reason.The table below compares the two. RS-485, which specifies bidirectional, half-duplex data transmission, is the only EIA/TIA standard that allows multiple receivers and drivers in "bus" configurations. EIA/TIA-422, on the other hand, specifies a single, unidirectional driver with multiple receivers. RS-485 parts are backward-compatible and interchangeable with their RS-422 counterparts, but RS-422 drivers should not be used in an RS-485 system because they cannot relinquish control of the bus.
RS-485 and RS-422 Standards
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thunks » QBasicFAQ » Calculating and Validating NMEA Checksums » CppBuilder » CMOS_C » The GPRMC Sentence » TurboCpp » BeginnersGuideToCurl » Curl Content Language » QbasicFAQ_Mouse » rs 485
RS-485
The RS-485 standard was developed jointly by two trade associations: the Electronic Industries Association ( ?EIA) and the Telecommunications Industry Association (TIA). The EIA once labeled all its standards with the prefix "RS" (Recommended Standard). Today, various extensions of the RS-485 standard accommodate a large variety of applications. The RS-485 and RS-422 standards have much in common, and are often confused for that reason.The table below compares the two. RS-485, which specifies bidirectional, half-duplex data transmission, is the only EIA/TIA standard that allows multiple receivers and drivers in "bus" configurations. EIA/TIA-422, on the other hand, specifies a single, unidirectional driver with multiple receivers. RS-485 parts are backward-compatible and interchangeable with their RS-422 counterparts, but RS-422 drivers should not be used in an RS-485 system because they cannot relinquish control of the bus.
RS-485 and RS-422 Standards
RS-422 RS-485
Mode of operation Differential Differential
Allowed no. of Tx and Rx 1 Tx, 10 Rx 32 Tx 32 Rx
Maximum cable length 4000ft length 4000ft length
Maximum data rate 10Mbps 10Mbps
Minimum driver output range ±2V ±1.5V
Maximum driver output range ±5V ±5V
Maximum driver
short-circuit current 150mA 250mA
Tx load impedance 54 100
input sensitivity ±200mV ±200mV
Maximum Rx input resistance 4k 12k
Rx input voltage range ±7V -7V to +12V
Rx logic high >200mV >200mV
Rx logic low <200mV <200mV
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