The MOS Technology 6509, an enhanced version of the popular
6502
The MOS Technology 6502 (typically pronounced "sixty-five-oh-two" or "six-five-oh-two") William Mensch and the moderator both pronounce the 6502 microprocessor as ''"sixty-five-oh-two"''. is an 8-bit microprocessor that was designed by a small ...
microprocessor
A microprocessor is a computer processor (computing), processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, a ...
, is capable of addressing up to 1
megabyte
The megabyte is a multiple of the unit byte for digital information. Its recommended unit symbol is MB. The unit prefix ''mega'' is a multiplier of (106) in the International System of Units (SI). Therefore, one megabyte is one million bytes ...
of
RAM
Ram, ram, or RAM most commonly refers to:
* A male sheep
* Random-access memory, computer memory
* Ram Trucks, US, since 2009
** List of vehicles named Dodge Ram, trucks and vans
** Ram Pickup, produced by Ram Trucks
Ram, ram, or RAM may also ref ...
via
bank switching
Bank switching is a technique used in computer design to increase the amount of usable memory beyond the amount directly addressable by the Processor (computing), processor instructions. It can be used to configure a system differently at diffe ...
. While numerous 6502-based processors can perform bank switching, they achieve this via separate logic. The 6509 has this logic on-
chip
Chip may refer to:
Food
* Chip (snack), thinly sliced and deep-fried gastro item
** Potato chips (US) or crisp (UK)
* Chips (fried potato strips) (UK) or french fries (US) (common as a takeout side)
* Game chips, thin chip/French fries
* Choco ...
.
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)
65xx microprocessors
MOS Technology microprocessors
8-bit microprocessors
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