Micropolis -- Floppy Disk Controller
This was the board that really put Micropolis on the
The controller contains the following major functional units:-
Control logic to interpret CPU selection and respond
to CPU commands.
A sector separator that separates sector and index pulses and keeps track of
each sector as it passes under the read/write head on 5 1/4" disks
Write logic that converts parallel-form bytes from the CPU to serial data
suitable for recording on the disk.
Read logic that converts the serial data from the disk to parallel-form
bytes for transfer to the CPU.
Bootstrap PROMs for reading sector zero of the system disk into RAM, then
starting the program in RAM.
Disk Data Format
Data is recorded on the disk in concentric tracks. The outermost track is
track zero. Each track is divided into 16 sectors. The beginning of each
sector is indicated by a sector hole punched in the disk. An index hole is
located halfway between the holes for sector 15 and sector zero. The sector
and the index hole are sensed by a photo transistor in the disk drive. Each
disk sector consists of a preamble, sync byte, header, data, a checksum,
and a post amble. Details are described in the manual.
The normal controller base address was C000H-FC00H but the board could be
jumpered to any 1K boundary. This was a large bite the 64K available address
Vector Graphic worked closely with Micropolis in the early days and utilized
this same board in their early systems.
The Vector Graphic manual for this board may be
As best I can tell it is identical to the Micropolis
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