MOS Technology 6502

6502AD (click to enlarge)

The MOS 6502 is an 8-bit processor that was originally developed by a team led by the engineer Chuck Peddle. It was introduced in 1975 and it is still being produced. It was produced by the following companies.

• California Micro Devices (GTE Microcircuits)
• Commodore Semiconductor Group (MOS Technology)
• Rockwell
• Synertek
• Western Design Center

Currently it is only produced by Western Design Center (WDC)

It was a popular choice of processor because of its low price and high capabilities. It was used in multiple early computers such as the Commodore 64, Commodore VIC-20, Apple II, BBC micro, and many others.

Internals

The 6502 had many revisions and derivatives. Most of the revisions have either enhanced its capabilities or have added new features.

Depending on the manufacturer, the fabrication process can be CMOS, HMOS and NMOS.

The 6502 has three registers, one main register and two index registers. The original MOS 6502 had 151 "legal" opcodes. Later version included more.

MOS 6502 registers

15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00 (bit position) Main registers   A Accumulator Index registers   X X index   Y Y index 0  0  0  0  0  0  0  1 SP Stack Pointer Program counter PC Program Counter Status register   N V - B D I Z C P Processor flags

Used in

• 1230, 1225, 1220
• DC509, DC5009: R6504 28-pin DIP variant with 13-bit address bus (8K address space)

Documents

• WDC 65C02 datasheet (Offsite)
• 6502 information site including datasheets and other derivative processors
• Wikipedia

Pictures

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