I create a SNES on FPGA. And now I tested several small games with simple LoROM mapper (Dr.Mario, Super Mario World 1, Tetris Attack, Battletoads, Tom and Jerry, Daffy Duck, Sim Sity). All tested games works well. But one game (Sim Sity) works with damaged sprites (and backgrounds, and objects).
I found that the problem disappears if I temporarily remove dram refresh mode in SCPU module. I'm thinking the problem in DMA. I can't understand how DMA should work during dram refresh cycle.
I found that the problem disappears if I temporarily remove dram refresh mode in SCPU module. I'm thinking the problem in DMA. I can't understand how DMA should work during dram refresh cycle.