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More importantly, the style of access changed. In the 6800, IX held a 16-bit address which was offset by an 8-bit number stored with the instruction and added to the address. In the 6502 (and most other contemporary designs), the 16-bit base address was stored in the instruction, and the 8-bit X or Y was added to it. [47]
The 65xx family of microprocessors, consisting of the MOS Technology 6502 and its derivatives, the WDC 65C02, WDC 65C802 and WDC 65C816, and CSG 65CE02, all handle interrupts in a similar fashion. There are three hardware interrupt signals common to all 65xx processors and one software interrupt, the BRK instruction.
The original 6502 has 56 instructions, which, when combined with different addressing modes, produce a total of 151 opcodes of the possible 256 8-bit opcode patterns. The remaining 105 unused opcodes are undefined, with the set of codes with low-order 4-bits with 3, 7, B or F left entirely unused, the code with low-order 2 having only a single ...
The CSG 65CE02 is an 8/16-bit microprocessor developed by Commodore Semiconductor Group in 1988. [1] It is a member of the MOS Technology 6502 family, developed from the CMOS WDC 65C02 released by the Western Design Center in 1983.
In 6502 assembly language, the above two instructions both accomplish the same thing: they load the value of memory location $12 into the .A (accumulator) register ($ is Motorola/MOS Technology assembly language notation for a hexadecimal number). However, the first instruction is only two bytes long and requires three clock cycles to complete.
This is the opcode table for the MOS Technology 6502 microprocessor from 1975. The 6502 uses 8-bit opcodes. Of the 256 possible opcodes available using an 8-bit pattern, the original 6502 uses only 151 of them, organized into 56 instructions with (possibly) multiple addressing modes. [1]
Microprocessors encode their instructions as a series of bits, normally divided into a number of 8-bit bytes.For instance, in the MOS 6502, the ADC instruction performs binary addition between an operand value and the value already stored in the accumulator.
The Mitsubishi 740 family has a processor core that executes a superset of the 6502 instruction set including many of the extensions added in the 65C02. There is a core set of new instructions common across all 740 family members, plus other instructions that exist in specific parts. [1]