SP336E

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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.