VFIR Coding
This topic discusses how IrDA miniport drivers and their infrared NICs code frames for transmission at Very Fast IrDA (VFIR) link speeds. The VFIR specification defines short-range low power operation at 16Mbps (half duplex). All VFIR devices are also required to support FIR and SIR operation.
For VFIR link speeds, an entirely different coding scheme, called HHH(1,13), is used. The letters HHH that represent this coding scheme are the initials of the three researchers who invented it. The HHH(1,13) coding scheme should always be implemented in hardware. For more information about HHH(1,13), see the publication Infrared Data Association Serial Infrared Physical Layer Link Specification available from IrDA.
The IrDA miniport driver's hardware can calculate the CRC to validate the frame. However, if hardware does not calculate CRC, the IrDA miniport driver must calculate CRC. For VFIR link speeds, a 32-bit CRC is used, which is the same as that used for FIR link speeds. An algorithm for calculating the 32-bit CRC is available in the publication Infrared Data Association Serial Infrared Physical Layer Link Specification.