[time-nuts] STEL 1175 vice 1173

Ed Palmer ed_palmer at sasktel.net
Wed May 14 14:11:51 EDT 2014


Hi Magnus,

Yeah, I like a challenge, but let's keep things reasonable! :)  The 
package conversion is easy to accomplish, the FPGA would be a real 
stretch for me, but reverse engineering the system code is more than I 
want to tackle - although I have thought about it!

Ed

On 5/14/2014 11:17 AM, Magnus Danielson wrote:
> Hi Ed,
>
> You could probably use a 32 bit DDS, but there will be a whole bunch 
> of little trimmings you would have to do in the CPU code which would 
> require quite a bit of (interesting) work. I would say it would be 
> beyond the scope of most folks.
>
> Cheers,
> Magnus
>
> On 05/14/2014 06:53 PM, Ed Palmer wrote:
>> Hi Corby,
>>
>> Thanks very much for the offer, but it looks like it would still be a
>> big project to use an '1175 to replace an '1173.  I think I'll have to
>> pass.
>>
>> The package difference (PLCC68 vs. PLCC44) would still require a
>> daughterboard of some sort.  I've learned a little over the past week
>> about NCOs and, if I'm right, reducing the clock speed from 45 MHz to 30
>> MHz would partially compensate for the 32 vs. 48 bit difference.  The
>> output frequency would be correct, but the waveform would have more
>> harmonics.  Since the clock is derived from a 90 MHz signal, the
>> reduction would be easy.  Whether that would have an adverse impact on
>> the operation of the Datum 4065A is way beyond me.  It looks like both
>> chips have a 12 bit output which is nice. The '1175 has more features
>> than the '1173.  I'd have to study the data sheet to see if they can be
>> configured to make the '1175 act like an '1173.
>>
>> For now, the plan is to try and source the '1173 in the 48-pin DIP
>> package and do a (relatively) simple daughterboard to adapt the
>> packages.  Even that will probably end up costing ~$150.  If that
>> doesn't work out, there's the possibility of an FPGA replacement. That
>> would likely allow replacing the AD9713 D/A converter as well as the
>> STEL-1173.  It turns out that an NCO is a standard application in the
>> FPGA world.
>>
>> Ed
>>
>> On 5/14/2014 9:13 AM, cdelect at juno.com wrote:
>>> Hi,
>>>
>>> I found two PLCC STEL 1175 in a rack mounted synthesizer I have.
>>>
>>> I'd be willing to sell the chips.
>>>
>>> Would they work?
>>>
>>> Cheers,
>>>
>>>
>>> Corby




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