[sdiy] Ancient Sequencer Project[was]Re: Art of electronics computer

[James Patchell]

It was pretty simple.  Keep in mind, in 1975 I was still in college.  
The thing was built using as much scrap parts as I had.  The only parts 
I purchased, which at the time, were very pricey, were four 256x1 pMOS 
ram chips.  That was all I could afford at the time.  The eight slide 
switches were for entering either a memory address (8 bits) or a data 
nibble (4 bits), depeding on which push button you pushed.  The memory 
was organized as 3 nibbles per sequence event.  Two nibbles made up an 8 
bit word that was sent to a DAC (just an R-2R ladder network) to be used 
as a control voltage, and the other nibble of the group went to a 74193 
down counter to be used to generate the duration of the sequence event.

     The whole thing was controlled by a sequential state machine made 
from 4000 series CMOS logic.  Or was it just TTL?...well, no matter.  
Because the memory was only 256 words, it would store only 85 steps.

     When I got my Paia 8700, I made a software version that ran on a 
6503.  I made an  expander for the 8700 that had an aditional 1K of ram 
and a pair of 6522 VIAs that helped the sequencer a bit.  The software 
version used 2 bytes per event, 8 bits for the control voltage, and 8 
bits for the duration.

     If I were going to do this today, I would use a micro processor 
with a built in DAC.

-Jim

On 1/8/2012 4:00 PM, Dan Snazelle wrote:
> Do you think you could explain the general concept?
>
> Thanks
>
> Sent from my iPhone
>
> On Jan 8, 2012, at 5:22 PM, James Patchell<patchell at cox.net>  wrote:
>
>> I wish I could post those as well.  Schematics for that project were lost a long time ago.  It would be fairly simple to duplicate with an AVR...
>>
>> -Jim
>>
>> On 1/8/2012 2:17 PM, Dan Snazelle wrote:
>>> That project you posted is really cool!!
>>>
>>>
>>> But what id love to see a schematic for (or notes or comments) is that sequencer you made in 75! That seems like endless fun
>>>
>>>
>>> Thanks!!
>>>
>>>
>>> Dan
>>>
>>>
>>>> I would think that trying to find 68008 would be a rather difficult task.  I used to use this chip quite a bit.  It was really fun.  Also, if you need a compiler for that chip, let me know.
>>>>
>>>> I have a midi Glockenspiel that uses a 68008 to do the Midi and control the solenoids that strike  the bars.
>>>>
>>>> http://www.noniandjim.com/Jim/midictl/midictl.html
>>>>
>>>> -Jim
>>>>
>>>>
>>>> On 1/8/2012 1:42 PM, Dan Snazelle wrote:
>>>>> I have built micro based stuff on breadboard....its great
>>>>>
>>>>> But i thought i might learn more about busses and memory this way....maybe thats nonsense
>>>>>
>>>>>
>>>>> Plus ive been reading all these byte backissues. :)
>>>>>
>>>>> Sent from my iPhone
>>>>>
>>>>> On Jan 8, 2012, at 4:09 PM, John Luciani<jluciani at gmail.com>    wrote:
>>>>>
>>>>>> Rather than building a computer based on a 68008 you may be better
>>>>>> of breadboarding an embedded system with a microcontroller. You can program any
>>>>>> uC in assembly language. You will also quickly gain experience with
>>>>>> other hardware
>>>>>> functions like A/D conversion, counters/timers, etc without having to
>>>>>> add hardware
>>>>>> to your breadboard.
>>>>>>
>>>>>> (* jcl *)
>>>>>>
>>>>>>
>>>>>> -- 
>>>>>> http://www.wiblocks.com
>>>>>>
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