MIR Coding
This topic discusses how IrDA miniport drivers and their infrared NICs code frames for transmission at Medium IrDA (MIR) link speeds. The MIR data rates are 0.576 Mbps and 1.152 Mbps (half duplex).
For MIR link speeds, definitions for BOF and EOF values are the same; both BOF and EOF are defined as 0x7E. To avoid ambiguity in the frame with BOF and EOF, rather than using an escape sequence as is done at SIR rates, a zero is inserted at MIR rates after any five consecutive one bits in all members except BOF and EOF. Because the process of inserting and stripping zeros at the bit level is highly processor-intensive, it is strongly recommended that this logic be implemented in hardware. At MIR link speeds, two BOF flags are required on every frame.
For MIR link speeds, the CRC used is the same as for SIR speeds. That is, for MIR link speeds, the IrDA miniport driver also typically calculates the CRC value rather than the driver's hardware.