MOS Technology 6507

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The 6507 is an 8-bit microprocessor from MOS Technology, Inc. It is a "cut down" version of their popular 6502. To reduce costs the 6507 included only thirteen address pins instead of the 6502's sixteen. This allowed the 6507 to address 8 KB of memory, which at the time (1975) was considered to be a lot. The omission of these lines allowed the 6507 to come in a smaller 28-pin package, instead of the 40 pins of the 6502.

In addition to the reduced address bus, the 6507 is also unable to service external interrupts, but is otherwise identical to the 6502. The 6507 was only widely used in two applications, the bestselling Atari 2600 video game console and the Atari 8-bit family floppy disk controllers for the 810 and 1050 drives. In the 2600, the system was further limited by the design of the cartridge slot, which allowed for only 4KB of external memory to be addressed (the other 4KB was reserved for the internal RAM and I/O chip). Most other machines, notably home computers based on the 650x architecture, used either the "full" 6502 or extended, rather than cut down, versions of it, in order to allow for more memory.

By the time the 6502 line was becoming widely used around 1980, ROM and RAM semiconductor memory prices had fallen to the point where the 6507 was no longer a worthwhile simplification; its use in new designs ceased at that point, though the Atari 2600 which contained it continued to be sold until the end of the 1980s.

Pin configuration

The 6507 uses a 28-pin configuration, with 13 pins in use for addressing, and 8 for data. The seven remaining pins are used for power, clock cycles, to indicate reset or ready, and control the read/write request from the CPU. There is no IRQ or NMI on the processor.


References

MOS 4510 · MOS 6501 · MOS 6502 · WDC 65C02 · Hudson HuC6280 · Ricoh 2A03 · MOS 6507 · MOS 6508 · MOS 6509 · MOS 6510 (and 7501, 8500, 8501) · MOS 8502 · MOS 65CE02 · WDC 65802 · WDC 65816 · Ricoh 5A22 · Nintendo SA-1

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