SuperSamX32

Super SAMx32

This repository contains the physical design for an enhanced replacement for the Motorola SAM MC6883 (SN74LS783/SN74LS785).

The design integrates the SAM, VDG and RAM into a single device

Introduction

The SAMx8, designed by Ciaran Anscomb, integrated the SAM and RAM functionality to provide a 512KB address space and operating video timing during double speed operation.

The design builds on that initial work to expand the address space to 2MB and integrate the VDG based on work performed by myself. The physical design is distinct to this project but the HDL includes an adaptation of Ciaran's work.

Minimum Required IO

• Single data bus (8 bit)
• Single address bus (16 bit)
• Oscillator input
• Quadrature Clock (Q/E)
• R/W
• Reset
• S (3 bits)
• A/G
• GM (3 bits)
• CSS
• HS/FS
• RGB (16 bit) - combined to 3 analog signals
• ROW (4 bits)
• Character data (8 bits)
• Character code (6 bits)

Total digital IO: 77 pins

Character ROM

The ROM data is held on an external EPROM, allowing for multiple sets to be available. Only 128 characters exist in each defined set. The inverse text capability is handled by providing normal and inverse data in the character set record

Without use of additional IO pins, the selection of the character set is only through external switching

Hardware Selection

The SAMx8 utilised the Xilinx XC95144XL - a 144 macro cell CPLD. The VDG replacement requires a Atmel 128 macro cell device by itself. Combining the two reduces some of the complexity but not enough to squeeze the design into a device from either family. The first appropriate device going up-scale is the Altera MAX II with 440 macrocells which offers a huge redundancy but equally offers a great deal of flexibility for further enhancement

Initial design work assumes the use of the Altera EPM570T144

License

This project is shared under the Create Commons Attributions-ShareAlike 4.0 International (CC BY-SA 4.0)

You are free to:

• Share - copy and redistribute the material in any medium or format
• Adapt - remix, transform, and build upon the material for any purpose, even commercially

The licensor cannot revoke these freedoms as long as you follow the license terms. Under the following terms:

• Attribution - You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use
• ShareAlike - If you remix, transform, or build upon the material, you must distribute your contributions under the same license as the original

No additional restrictions - You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits