SP336E Datasheet, PDF (24/30 Pages) Exar Corporation – 3.3V - 5V PROGRAMMABLE RS-232/RS-485/RS-422 SERIAL TRANSCEIVER

SP336E
3.3V - 5V PROGRAMMABLE RS-232/RS-485/RS-422 SERIAL TRANSCEIVER
REV. 1.0.0
RS-232 to RS-485 Translator
SP336E can be used to implement a single-chip RS-232 to RS-485 translator function. Both full-duplex (4-wire
RS-485) and half-duplex (2-wire RS-485) configurations are shown. RS-485 is capable of communicating on
data cables up to 4000 feet (1200 meter) which makes it an ideal interface for extending the reach of short-
range serial ports like RS-232. The configurations shown can be used to connect directly to existing PC type
RS-232 serial ports to enable extended-reach communication.
The RTS signal (circuit CA or 105) is used as a transmit direction control signal for half-duplex. The ON
condition puts the repeater into transmit mode and inhibits receive. On a half-duplex channel RxD should be
held in MARK state (binary 1) when receiver 3 is inactive. Driver 1 on the SP336E can be used to generate
DSR or CTS signal to indicate to the host terminal that the translator is powered-on and ready.
Shutdown Modes
SP336E features two shutdown modes. In mode 111 (full shutdown) all drivers and receivers are at high
impedance. In mode 110, all drivers are tri-state but all four receivers remain active. In modes 101 and 100 two
differential receivers can be kept active while the differential drivers are tri-stated using the Tx_EN inputs.
FIGURE 25. RS-232 / RS-485 TRANSLATOR FULL-DUPLEX CABLE-EXTENDER (MODE 011)
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