I must warn that designing a mcu is unlike building a house out of lego bricks. If you treat all the individual circuits as standard building blocks, you'd find out later that you would not be able to fit them together once your architecture and instructions set are defined.
If you want to make your job easier, you can always take a subset of the 8051 instructions and make a smaller model with less memories and 1 or 2 8-bit ports. A mcu with 2KB ROM and 256 bytes of RAM is easier to do than one with 32KB ROM and 32KB RAM.
Allen
If you want to make your job easier, you can always take a subset of the 8051 instructions and make a smaller model with less memories and 1 or 2 8-bit ports. A mcu with 2KB ROM and 256 bytes of RAM is easier to do than one with 32KB ROM and 32KB RAM.
Allen