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The methods by which the MPU state is preserved and restored within an ISR will vary with the different versions of the 65xx family. For NMOS processors (e.g., 6502, 6510, 8502, etc.), there can be only one method by which the accumulator and index registers are preserved, as only the accumulator can be pushed to and pulled from the stack. [5]
Interior of the 6502 Second Processor. The 6502 Second Processor (using a 6502C) was clocked at 3 MHz, a full 50% faster than the 6502 inside a BBC Model B, and also had 64 KB of RAM, of which typically 30–44 KB was free for application data (compared to as little as 8.5 KB on an unexpanded Model B in graphics mode, or only 5.75 KB with the disc interface).
The 6502 instruction set includes BRK (opcode $00), which is technically a software interrupt (similar in spirit to the SWI mnemonic of the Motorola 6800 and ARM processors). BRK is most often used to interrupt program execution and start a machine language monitor for testing and debugging during software development.
MOS Technology 6502: Linux, Windows, macOS: SynAssembler Synapse Software: No Proprietary: MOS Technology 6502: Atari 8-bit: VASM: Volker Barthelmann, Frank Wille No Free MOS Technology 6502: various xa65: Cameron Kaiser, André Fachat Yes GPL MOS Technology 6502, WDC 65C02, WDC 65C816: Linux, various XASM: Piotr Fusik Yes Free MOS Technology ...
Merlin is a MOS Technology 6502 macro assembler developed by mathematics professor Glen Bredon for the Apple II under DOS 3.3. It was published commercially by Southwestern Data Systems, [1] later known as Roger Wagner Publishing. Merlin continued to be updated as successors to the 6502 became available: first the 65C02 and later the 65816 and ...
Free and open-source software portal; GeckOS is a multitasking operating system for MOS 6502, and compatible processors such as the MOS 6510. [1] The GeckOS operating system is one of the few successful attempts to implement a Unix-like operating system on the 6502 architecture.
VisiCalc ("visible calculator") [1] is the first spreadsheet computer program for personal computers, [2] originally released for the Apple II by VisiCorp on October 17, 1979. [1] [3] It is considered the killer application for the Apple II, [4] turning the microcomputer from a hobby for computer enthusiasts into a serious business tool, and then prompting IBM to introduce the IBM PC two years ...
Apple wanted an MPU that would be software compatible with the 6502 then in use in the Apple II but with the ability to address more memory, and to load and store 16 bit words. The result was the 65C816, finished in March 1984, with samples provided to both Apple and Atari in the second half of the year and full release in 1985. [ 5 ]