VIC-20 Block Diagrams
Here are the block diagrams, that I have drawn in Inkscape. They are based on the file vic20bus.gif, that I have found at zimmers.net.
Beside the power supply circuit, which is the most obvious difference between the (older) two-prong VIC-20 (ASSY 324003) and the VIC-20CR (ASSY250403, with the DIN power jack) and the migration of 4 of the 5kB RAM into the 2116 type 2kB RAMs, I have found other differences, which I find interesting.
1. The VIC-20CR has an Audio Input on the Expasion Port (pin Y).
2. The VR/W signal (Read/Write for the VIC), which asserts the internal RAM, is generated in a different way.
Beside the power supply circuit, which is the most obvious difference between the (older) two-prong VIC-20 (ASSY 324003) and the VIC-20CR (ASSY250403, with the DIN power jack) and the migration of 4 of the 5kB RAM into the 2116 type 2kB RAMs, I have found other differences, which I find interesting.
1. The VIC-20CR has an Audio Input on the Expasion Port (pin Y).
2. The VR/W signal (Read/Write for the VIC), which asserts the internal RAM, is generated in a different way.
VIC-20 ASSY 324003 (click to enlarge)
VIC-20CR ASSY 250403 (click to enlarge)
Here are the (inkscape/vector graphis) source files (GPL-3.0 License):
● VIC20_Block_Diagram.svg
● VIC20CR_Block_Diagram.svg
You also might have to install the Microgramma D Extended font to get an undistorted Inkscape Image.
Please respect my work of many hours and if you want to use these files, refer to my website.