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Tiny CPU Architecture

As promised, here’s the Tiny CPU architecture diagram. SP is the stack pointer, and is 6 bits, providing a 64-entry stack. EA is the effective address, used for data load/store from absolute or computed addresses. PC is the program counter. The accumulator A and index register X are the only data registers. The datapath is controlled by a state machine and combinatorial logic, using the current opcode, state, and arithmetic/logic flags as input.

The diagram glosses over a few details, such has how the 8-bit data bus is connected to 10-bit address registers. Where busses and registers of differing sizes are connected, additional logic selects the low or high byte as needed.

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