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The 6502 programming manual thus requires each ISR to reset or set the D flag if it uses the ADC or SBC instruction, but occasionally a human programmer may mistakenly omit to do this, causing a bug. For example, the Commodore 64 's KERNAL did not correctly handle this processor characteristic, requiring that IRQs be disabled or re-vectored ...
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 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.
It has 92 instructions, an 8-bit data bus, a 16-bit accumulator, and a 24-bit address bus. The CPU runs between 1.79 MHz and 3.58 MHz, and uses an extended MOS Technology 6502 instruction set . Major features
An instruction set architecture (ISA) is an abstract model of a computer, also referred to as computer architecture.A realization of an ISA is called an implementation.An ISA permits multiple implementations that may vary in performance, physical size, and monetary cost (among other things); because the ISA serves as the interface between software and hardware.
The System/360, [3] ARM, POWER/PowerPC, 6502, MSP430, COP8, Am29000, i960, and 88000 processors use this convention. The 6502 is a particularly well-known example because it does not have a subtract without carry operation, so programmers must ensure that the carry flag is set before every subtract operation where a borrow is not required. [4]
The Western Design Center (WDC) 65C02 microprocessor is an enhanced CMOS version of the popular nMOS-based 8-bit MOS Technology 6502.It uses less power than the original 6502, fixes several problems, and adds new instructions.
Although source compatible with the earlier Motorola 6800, the 6809 offered significant improvements over it and 8-bit contemporaries like the MOS Technology 6502, including a hardware multiplication instruction, 16-bit arithmetic, system and user stack registers allowing re-entrant code, improved interrupts, position-independent code, and an ...