MOS Technology 6509
The MOS Technology 6509, an enhanced version of the popular 6502 microprocessor, is capable of addressing up to 1 megabyte of RAM via bank switching. While numerous 6502-based processors can perform bank switching, they achieve this via separate logic. The 6509 has this logic on-chip.
Passing data between different banks requires use of the register at $1 which selects the banks to be read from and written to via LDA (zero page), Y and STA (zero page), Y CPU opcodes. The register at $0 selects the bank where the CPU fetches instructions from, which will default to 15 ($F) on power up.
The 6509 has a reputation for being difficult to program, due to its bank switching scheme. It is used in the Commodore CBM-II line of computers.
References
Further reading
External links
- MOS 6509 datasheet (GIF format, zipped)
- MOS 6509 datasheet (PDF format)
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- 6502 (and 6501, 6503, 6504, 6505)
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- 8502 (and 7501, 8500, 8501)
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- 65C816 (and 65C802)
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