RXD(x) will receive a single byte of data that is shifted as an asynchronous serial stream. This function is similar to SERIN, but is a more efficient implementation.
RXD(x) will return 0-255 if there was data present. or -1 (&HFFFFFFFF) if there is no serial stream available on SIN. The hardware UARTx is used, so the CPU is not tied up, and bytes are buffered up to 256 bytes being received by an interrupt routine
SuperPRO or PROplus--
These devices support 4 UARTs, pin assignments in the Hardware Info
BASICchip or ARMmite--
Pin labeled RXD0 on the schematic, UART0 of the LPC2103. Data is always positive true.
Baudrates can be up to 115.2 Kbaud.
The compiler is also backward compatible with the syntax -- x = RXD0 , x= RXD , or x= RXD1