Table of Contents
The FATVIC has all the features that the 6560 and 6561 has.
FATVIC is a drop-in replacement for 6560 or 6561. It automatically adjust to the clockfrequency of the NTSC (6560) or the PAL /6561) version.
It also has the same physical size as the 40 pin DIP package, with a clear notch for correct orientation.
The electronics is basically buffers for 5V to 3.3V level shifting, the FPGA (Lattice ECP-5) with NOR FLASH for configuration, 24bit stereo codec, power regulators for core and auxiliary voltages and finally some analog parts for composite and VGA video.
The VGA is connected to a ZIF socket. It has a small Rigid FPC with a mini DIN that sits in a dummy DIN connector. In this way it can use the existing hole in the bread-bin enclosure, for nice look and feel.
Apart from the drop-in replacement funtionallity the FATVIC has the following target features.
Memory
With the addition of the FATVIC director in place of the 74LS138 BLKn decoder, the memory can be extended.
Inside the FPGA are 8k SRAM for the BLK0, there is also SRAM for the CHARROM as well as sprite information. All of these 8k are addressable by the FATVIC.
The director adapter also disables the cartridge ports RAM1,2 and 3 chip select signals.
The Color SRAM is 8 bit wide and holds additional information.
The FATVIC has 32 additional registers that is hidden at power up and reset. It is 100% compatible.
Audio / Video
VGA output through a mini DIN mounted in the same space as the ordinary audio/video DIN connector. Changes done are reversable.
It also has a 24bit stereo codec.
Graphics
The FATVIC has some additional features for graphics. First of, it has 16 times the color SRAM for a new color for each scanline instead of each 8 scanlines. This for compatibility with various modifications and software.
There is a enhanced text mode display with 40 x 25 and 80 x 25 characters, with the same character set as normal.
Since color RAM is 8-bit I have thought about extending this to support;
- 2 sets of fonts, which would make it possible to have the standard ASCII characters as well as custom, not either or.
- Automatic inverse of video.
- 2 additional bits for 4 different palettes (including multicolor).
Besides that it is not really set in stone what I will go for. It is a matter of walking a fine line between keeping this a VIC-20 with slight enhancements, and making a Frankensteins monster, just because. For that I have the NeoCore 65C816 based computer.
But I have some ideas for both extended tile management, a bitmap mode with hardware accelerated drawing functions and block move. Also 8-32 sprites on the drawing board.
The future will see what I end up doing. Since much of this will be reused for NeoCore, there is not a question of development resources.