Uses 4 of the the NXP SPI/UART bridge chips, P/N SC16IS762 (or similar).
Total of 8 hardware UARTs per board.
It's possible to have 4 boards per Arduino system, for a total of 32 UARTs.
Supports any mix of RS-232 (using a YASC2/6/8 interface boards), or RS-485 (using a YASC485 interface board).
On-board 3.3V regulator. Can be linked to Arduino 3.3V rail via a jumper.