Re: 6702 chip

The even.odd register appears to work this way:

1) It is a "not even/odd" register. The logic is simpler.

2) The low bit of the input is ANDed with the "not even/odd" register.

3) If the result is 0, the number is not accepted, and the low bit is 
transferred to the "not even/odd" register through a gated inverter.

4) If the result is 1, the number is accepted and is processed as 
described below.  At the point that the input is transferred to the last 
number register, the low bit is also transferred to the "not even/odd" 
register through an inverter, probably the same inverter as in 3 above.
This would be done by either a dual gated inverter, or an OR gate before 
the inverter.


This is now a complete description of the internal workings of the 6702.


Have I missed anything?



On Sun, 22 Jul 2012, William Levak wrote:

> On Tue, 17 Jul 2012, William Levak wrote:
>
> I have analyzed the logic of the chip's operation, and tried a number of 
> variations.  The last number register and the flip flops are initialized
> to 214 and the cannot be moved forward or backward in the logic stream. If 
> they are, then subsequent output is wrong.  It's like a CRC.  Not only must 
> the number be right, but the position in memory must be right also.
>
> This would then mean that operation does not begin with the shift registers 
> outputing to the flip-flops. This step is at the end of the cycle.  Operation 
> would begin with the flip-flops being loaded with 214, which would also send 
> 214 to the output register.
>
> Also if we make the even/odd register a not even/odd register, then 
> everything else is initialized to 0.
>
> This is simpler. The revised chip operation is:
>
> INITIALIZATION:
>
> The flip-flops and last number register are set to 214.
>
> Everything else is set to 0.
>
> OPERATION:
>
> 1.  The flip-flops output to the output register.
>
> 2.  The chip waits for input.  If the input is odd and the not even/odd
>    register is 1, continue below.  Otherwise transfer the complement
>    of the low bit of the input register to the not even/odd register, and
>    continue waiting for input.
>
> 3.  Exclusive or the input with the last number register.  Exclusive or
>    that result with the current position of the shift registers.
>
> 4.  Shift the shift registers one position, and copy the input register to
>    the last number register.
>
> 5.  Output the current position of the shift registers to the output
>    register.
>
> 6.  Go to step 1. and continue indefinitely.
>
>
> I have run more than 4000 randomly generated numbers through this sequence, 
> and it works perfectly.
>
> I have not been able to pin down exactly when the not even/odd register is 
> set.
>
>
> wlevak@sdf.lonestar.org
> SDF Public Access UNIX System - http://sdf.lonestar.org
>
>      Message was sent through the cbm-hackers mailing list
>

wlevak@sdf.lonestar.org
SDF Public Access UNIX System - http://sdf.lonestar.org

       Message was sent through the cbm-hackers mailing list