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Floppy Disk Controller: Difference between revisions
Old content of TDR section is BS - I have a floppy tape drive that still works. Added Tape Drive Register documentation.
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(Old content of TDR section is BS - I have a floppy tape drive that still works. Added Tape Drive Register documentation.) |
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== Overview and Documentation ==
The Floppy Disk Controller (FDC) is a (legacy) device that controls '''internal''' 3.5/5.25 inch floppy disk drive devices on desktop x86 systems.
There are a range of chips that have been produced for this function which include: 8272A, 82078, 82077SL & 82077AA. The 82077AA is the most
▲Of these chips, the 82077AA is the most advanced, and has been produced since 1991. For more recent systems, a model of that chip has been embedded in the motherboard chipset.
(So pay close attention to that datasheet, below.)
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They are the following:
=== FIFO
FIFO: The FIFO register may not have a 16byte buffer in all modes, but this is a minor difference that does not really affect its operation.
== Tape Drive Register ==
TDR: The Tape Drive Register is a R/W register which is identical in all modes. According to the documentation for the Intel 82077AA, the two least significant bits form a number between 1 and 3 (0 is an invalid value, drive 0 may not be selected) that assigns tape support to one particular drive out of four total drives. It is probably irrelevnant for modern uses, is not supported by any emulator and is probably not worth implementing support for unless you have all the real hardware to test this functionality on.
=== DOR bitflag definitions ===
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