S100 Computers

Home S-100 Boards History New Boards Software Boards For Sale
Forum Other Web Sites News Index    
Micropolis -- Floppy Disk Controller

This was the board that really put Micropolis on the map.

Micropolys FDC

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 space.

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 obtained here.  As best I can tell it is identical to the Micropolis manual.


Other Micropolis  S-100 Boards


This page was last modified on 07/28/2014