The 2150 implements the DTE side (the 2155 does DCE) of IrDA's IrComm protocol (9-wire cooked service class, in this device). This includes the TinyTP, IrLMP, IrLAP layers of the IrDA Standard protocol stack. It also handles some of IrPHY. Here's a link to the datasheet.

There are also appnotes on the Microchip website on the subject of the development board.