HuC6280

The HuC6280 8-bit microprocessor is Japanese company Hudson Soft's improved version of the WDC 65C02 CPU, an upgraded CMOS version of the popular NMOS-based MOS Technology 6502 8-bit CPU manufactured for Hudson by Seiko Epson. The most notable product using the HuC6280 is NEC's PC Engine video game console.

The HuC6280 contains a 65C02 core which has several additional instructions and a few internal peripheral functions such as an interrupt controller, a memory management unit, a timer, an 8-bit parallel I/O port, and a programmable sound generator. The processor operates at two speeds, 1.79 MHz and 7.16 MHz.

The HuC6280 has a 64 KB logical address space and a 2 MB physical address space. To access this entire memory space, the HuC6280 uses an MMU (Memory Management Unit) that splits the memory space into segments of 8 KB. The logical address space is split as follows:

Each logical 8 KB segment (or page) is associated with an 8-bit register (MPR0-7) that contains the index of the 8 KB segment (or bank) in physical memory to map in this page. Two special instructions are used to access these registers:

TAMi, transfer the content of the accumulator (A) into an MPR register (0-7).

TMAi, transfer an MPR register into the accumulator.

The PSG provides 6 sound channels, which can be conveniently paired according to the functionality they provide:

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