This week I worked with Adolfo to get the system onto the FPGA. I was setting up the needed functions on the FPGA through the Megafunction Wizard. We realized that combinational read was not possible using the RAM function so we needed to go back to simulation because our machines can not handle having arrays of that size. So I focused on finding a workaround. Originally we tried using the negative edge of the clock. This worked except in the case where there was a consecutive read and write to the same location. Then we tried giving it a faster clock and that broke our logic. Logically, we knew that the faster clock should work so we looked at the areas that were failing and saw it was a memory to memory transfer, so we adjusted the logic and made small timing changes and we were able to get it to work.
While Adolfo worked on the PPU and the system worked in simulation, the next thing was to support more games. To do this I implemented a memory controller that looked to see which setup the game was expecting. This allowed the games to extend their memory by being able to switch between different ROM and RAM bits. I worked on the controller that currently supports 2 out of the 3 main memory bank configurations. Depending on how these 2 work out, I might be able to get to the third one but that is the rarest of the setups.
Currently, I’m working with Adolfo to get Tetris running in simulation so we can put it on the board. Since our simulation setup matches the one we have on the FPGA, we hope to have everything on the board smoothly.
Goals for next week:
- Get Tetris, Dr. Mario and a game that uses MBC1 running on the FPGA
- Polish MBC3 and run a game