Re: 6702 chip

From: Rob Clarke <crock_at_clarke-family.org.uk>
Date: Sat, 12 May 2012 12:17:26 +0200
Message-ID: <4FAE38B6.1090206@clarke-family.org.uk>
 > Writing 00100001 results in 11110111 and bit 4 now counts with a 
period of 3.

obviously I meant bit 5 here.

On 12/05/2012 12:06, Rob Clarke wrote:
> Looks to me like the seed value is EOR'd with the written odd value 
> and only the counters for those bits are incremented.
>
> Given a seed of 214 - 11010110
>
> Writing 00000001 results in 11010111 and bits 5 & 3 do not count.
>
> Writing 00000011 results in 11010101 and bit 5,3 & 1 do not count.
>
> Writing 00001001 results in 11011111 and bit 3 now counts with a 
> period of 8.
>
> Writing 00100001 results in 11110111 and bit 4 now counts with a 
> period of 3.
>
> Rob
>
>
> On 12/05/2012 10:42, William Levak wrote:
>> On Sat, 12 May 2012, William Levak wrote:
>>
>>> I don't think it very likely that a chip the size of a 6702 can do 
>>> an actual divide.
>>
>> Not divisions; simple counting circuits, the intervals as Kajtar 
>> Zsolt described.
>>
>> Starting number, 214
>>
>> 128 toggled every 2 numbers
>>  64 toggled every 5 numbers
>>  16 toggled every number
>>   4 toggled every 7 numbers
>>   2 toggled every 3 numbers
>>   1 toggled every 6 numbers
>>
>> The pattern repeats every 420 numbers. (I neglected that 14 and 60 
>> have a common factor).
>>
>> Each operation affects only one bit, the whole chip would require 8 
>> counting circuits and perhaps a couple registers.  The output would 
>> require a latched register.
>>
>> This is from writing 0, followed by 1. Now that I have a formula, I 
>> can test what other numbers might do.
>>
>>
>> wlevak@sdf.lonestar.org
>> SDF Public Access UNIX System - http://sdf.lonestar.org
>>
>>       Message was sent through the cbm-hackers mailing list
>
>
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Received on 2012-05-12 11:00:32

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