Table of Contents
This is a short note on the different memories and the changed memory mapping of the VIC NX compared to the original.
CPU
The VIC NX can run with both the original 6502 or the modern CMOS variant 65C02. For the former you also need to mount the jumper above the CPU socket.
UART
There is also a true UART capable of runing up to 1Mbps, though the CPU will not be able to shuffel all that data.
CPLD
The main part in the middle is the CPLD called Dionysos that handles all the memory managment and selection. Including registers for various options and banking.
BLK0/4 and the VIC chip
BLK0 has full 8kByte compared to the original VIC 20.
The 3kByte at $0400 - $0FFF can be enabled/disabled, but not write protected. It is not routed to the cartridge port if disabled.
This memory also holds the CHARROM although in SRAM then. It also holds SRAM for IO#2 IO #3. These can be individually enabled/disabled and write protected. If disabled the corresponding cartridge chip select pin will be activated when addressed.
A main difference between VIC NX and the original VIC 20, is with this memory. This memory, including the 3kBytes at $0400 - $0FFF and IO #2/3 can be reached by the VIC chip.
Since the 4kByte CHARROM at $8000 - $8FFF also are writable it leaves for some exiting possibilities.
BLK 1, 2, 3 and 5
There is 32kByte SRAM for BLK1, 2, 3 and 5.
There is no bank registers for these. I have not seen any use for more memory than the 8k for each slot. However, all blocks kan be individually enabled/disabled as well as write protected. If disabled the corresponding cartridge chip select pin will be activated when addressed.
BLK 6/7
Last we have 512kByte NOR FLASH for BLK6/7. This is splitted in two parts. One for configuration mode and one for the normal mode.
There is one bank register for BLK6 and another for BLK7. Both are 32 bits wide.
It is also totally seperated in configuration mode.
S-Video
The VIC NX includes a Y/C signal for video. This seperates the luminans and chroma into two seperate pins. This is usually called S-Video (or sometimes S-VHS since it started appearing around the introduction of SVHS).
PAM4
There is also an experimental PAM4 encoder that encodes A14 and A15 on the NC (Pin 20) pin on the VIC 20 cartridge port. This is meant for cartridges that need the full addressbus for their use.
