First post!
Hi guys, i'm designing a 16 color composite video output game console. It just loads one game at the moment by having its EEPROM flashed. It has 32KB RAM (I could add another chip but I want to keep it simple/minimal for now). The ROM and RAM are together on one IC.
I'm using the Z80180 processor because it has more IO lines and can handle a clock frequency twice that of NTSC, so I can have to generate the HSYNC and VSYNC as well as output pixel data through address lines A15-A18. The RGBI values are converted to an analog voltage signal using a resistor array as a DAC.
The board runs off USB MICRO power plug (eg. phone charger). It has support for two 4-button controllers, which I will probably have to custom make with simply a bunch of buttons.
You'll also notice a 4007 logic inverter IC, this simply inverts the memory request bit from the processor, so whenever the memory is not being accessed, there is a direct data line open to read from the handheld controllers (they are the X inputs on the right hand side). This is my design and needs checking!
Before I start building this thing. I wanted to get some other opinions on if it looks like it might work. It's my first microprocessor design, so I imagine there are some things wrong. Rip it apart and ask me questions please. It's somewhat inspired by the Uzebox - especially the dedicated video output lines and timing. The code will be somewhat similar to that project. Perhaps in the future I can interface an SD card or something like they did.
The main thing I'm concerned about is the time taken to write bytes to the EEPROM and how to handle the delay. Can I make the processor wait until the EEPROM has finished reading?
Full schematic attached. Thanks for the help!
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