Ricoh 2A03 Core

This core implements a Ricoh 2A03, a variant of the MOS 6502 microprocessor that was used in the Nintendo Entertainment System and Famicom. Additional variants, like the Ricoh 2A07, were used in some models of the system, such as the PAL NES.

Reference: mos_6502

Subpages

• Subunit organization
• Clocks
• Signals
• 6502 Datapath
• 6502_Registers

A note on signal names

I use expanded signal names for readability and to keep what's left of my sanity intact when working on this project. However, the 6502 is inherently a silicon chip and while there have been a number of efforts to document silicon traces, registers, and other circuitry, there's no 'real' standard that I can tell.

One commonly used reference is a block diagram prepared by Dr. Donald Hansen and presented as part of a paper he presented in 1995 titled "A VHDL Conversion Tool for Logic Equations with Embedded D Latches." 1 This diagram documents the silicon at a low level and is said to be based on original engineering documents created at MOS Technology in the 70s. 2

As such, when naming a signal I will start with a name that makes sense to me, but will also suffix it with the label in Dr. Hansen's block diagram to allow for easier correlation between designs and HDL.

References