RE: 6510 CPU extensions

ncoplin_at_orbeng.com
Date: 2002-04-30 03:55:01

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    >What about the 6509? That is a 6502 with the difference that it has 
    >4 more address lines. The output values of the 4 address bits is
    >determined by the values of register 0 and 1. register 1 is used for 
    >the data load and store operations in the lda (),y and sta (),y 
    >opcodes and reg. 0 otherwise. (r0/r1 maybe vice versa, but in principle
    >that is it).
    
    This chip is indeed and interesting one. The theme could be extended to
    include a full 8-bit paging offset, allowing 16MB rather than 1MB access.
    For the setting of the register one of the illegal fatal codes could be used
    as the operand.
    
    
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