This part is a kind of semiconductor called MAX3140.

Function of this product has SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers.

Manufacturers : Maxim

Image and pinout :

Some of the text within the PDF file :

19-1453; Rev 0; 6/99 SPI/MICROWIRE-Compatible UART with Integrated True Fail-Safe RS-485/RS-422 Transceivers General Description The MAX3140 is a complete universal asynchronous receiver-transmitter (UART) and a true fail-safe RS485/RS-422 transceiver combined in a single 28-pin QSOP package for space-, cost-, and power-constrained applications. The MAX3140 saves additional board space as well as microcontroller (µC) I/O pins by featuring an SPI™/QSPI™/MICROWIRE™-compatible serial interface. It is pin-programmable for configuration in all RS-485/RS-422 networks. The MAX3140 includes a single RS-485/RS-422 driver and receiver featuring true fail-safe circuitry, which guarantees a logic-high receiver output when the receiver inputs are open or shorted. This feature provides immunity [ ... ]

MAX3140 PDF Datasheet Download