How is Nibble and Byte mode implemented?
Both the Byte Mode and Nibble Mode of operation are implemented in software only. The Byte Mode of operation requires that the parallel port is capable to receive data using all eight data lines. For both modes only a polled mode of operation is provided (with a programmed I/O-based method of data transfer), therefore no IRQ or DMA channel need to be configured. I noticed in the documentation that there is only support for reverse channel transfers in EPP mode — does the driver not support reverse channel transfer in ECP mode? As I understand, IEEE1284 allows the peripheral device to send a reverse channel request in ECP mode to allow it to communicate on a channel other than the current forward channel. The IEEE 1284 Standard provides for reverse channel information in ECP mode, but the host chip manufacturers did not put in any way to receive this information. Microsoft did not see a reason for this, so they refused to support it. So, although it is part of the standard there is no
