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6502 Micro Processors

The 65xx microprocessor was produced in a surprising number of variants, the smaller versions traded address space against interrupts and other functions.   Today, only the basic design, the 6502 is remembered.

Two series were produced, the 650x, which had a clock on the chip and the 651x series, which had an external clock.   This latter was intended for use in multi chip applications where accurate synchronisation was important.

What is interesting, is that it was considered worthwhile at the time to produce so many variants in each series to reduce the cost of the final product.   The designers could have had little insight then into the enormous price reductions that were soon to come.

65xx Series Micro Processors
Processor Pins Address Space Features
6502 40 64K
  • IRQ interrupt
  • NMI interrupt
  • On chip clock
  • SYNC signal (can be used for single instruction execution)
  • RDY signal (ditto single cycle)
  • Two phase output clock
6503 28 4K
  • On chip clock
  • IRQ Interrupt
  • NMI Interrupt
6504 28 8K
  • On chip clock
  • IRQ Interrupt
6505 28 4K
  • On chip clock
  • IRQ Interrupt
  • RDY Signal
6506 28 4K
  • On chip clock
  • IRQ Interrupt
  • Two phase clock output
6512 40 64K
  • IRQ Interrupt
  • NMI Interrupt
  • RDY Signal
  • SYNC Signal
  • Data Bus Enable (pin 36)
6513 28 4K
  • Two phase clock input
  • IRQ Interrupt
  • NMI Interrupt
6514 28 8K
  • Two phase clock input
  • IRQ Interrupt
6515 28 4K
  • Two phase clock input
  • RDY Signal

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28-Jan-2002
Revised: 27-May-2006 17:39
Text Copyright © 2002 A. Audsley, All Rights Reserved