MOS Technology 6502

MOS Technology 6502

General information
Launched	1975
Common manufacturer(s)	MOS Technology
Performance
Max. CPU clock rate	1 MHz to 3 MHz
Data width	8 bits
Address width	16 bits
History
Predecessor(s)	Motorola 6800
Successor(s)	MOS Technology 6510 WDC 65C02 WDC 65C816

The MOS Technology 6502 is an 8-bit processor based off the Motorola 6800. The 6502 was singlehandedly responsible for the home computing revolution, allowing for the development of some of the most influential home computers of the era, including Commodore 64.

Design

Registers

Zilog Z80 registers

15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 (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 Processor Flags

The 6502, just like the 6800, has a limited set of registers including a single 8-bit accumulator (A), two 8-bit general registers (X and Y), an 8-bit stack pointer (SP) and a 16-bit program counter (PC).

Flags

• Negative (N), set if the result is negative.
• Overflow (V), set if .
• Break (B), set if .
• Decimal (D), set if .
• Interrupt disable (I), set if .
• Zero (Z), set if the result is zero.
• Carry (C), set if the last addition operation resulted in a carry, or the last subtraction operation resulted in a borrow.