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Old 2nd February 2006, 09:12 AM   #1
poynton is offline poynton  United Kingdom
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Default PCM1733 Interfacing

Hi.

I have some PCM1733 DACs.

The data sheet states these are 18-bit dacs with a built in? 8x oversampling filter.

The input is I2S.

How can I interface these to a 16-bit I2S signal eg to replace theTDA1541 and SAA???? in an old Philips cd-p?

Would I have to introduce extra clocks for the 2 extra bits?

Andy
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Old 3rd February 2006, 03:05 PM   #2
tmblack is offline tmblack  United Kingdom
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Probably affects the MSB, so clock 2 for proper volume.
Why not get the 16 bit version of the DAC?

And whats wrong with Phlips TDA1541?

Tom

EE
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Old 3rd February 2006, 03:14 PM   #3
poynton is offline poynton  United Kingdom
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Quote:
Originally posted by tmblack
Probably affects the MSB, so clock 2 for proper volume.
Why not get the 16 bit version of the DAC?

And whats wrong with Phlips TDA1541?

Tom

EE

TDA1541 - Nothing at all !!

I just have 5 pcm1733. I was thinking of making up a small board to replace the TDA1540 in an old cd-p for fun but as I said, I do not know how to interface.
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Old 3rd February 2006, 05:03 PM   #4
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Default Its the datasheets,.................

Quote:
Originally posted by poynton
Hi.

I have some PCM1733 DACs.

The data sheet states these are 18-bit dacs with a built in? 8x oversampling filter.

The input is I2S.

How can I interface these to a 16-bit I2S signal eg to replace theTDA1541 and SAA???? in an old Philips cd-p?

Would I have to introduce extra clocks for the 2 extra bits?

Andy

You are replacing one I2S bus device with another, it as simple as it gets, even a six sigma black belt can do it. The position of the MSB is fixed regardless of wordlength and the clock is continuous. Add 256Fs MCLK and you are done.


Quote:
Originally posted by poynton

I was thinking of making up a small board to replace the TDA1540
The TDA1540 is not an I2S bus device.
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Old 3rd February 2006, 05:28 PM   #5
poynton is offline poynton  United Kingdom
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Default Re: Its the datasheets,.................

Quote:
Originally posted by rfbrw

You are replacing one I2S bus device with another, it as simple as it gets, even a six sigma black belt can do it. The position of the MSB is fixed regardless of wordlength and the clock is continuous. Add 256Fs MCLK and you are done.
Thats what I thought. I was wanting to replace the SAA7220 ( 4x filter ) and TDA1541 with the pcm1733 (8x filter). What worries me is the specs. for the PCM1733 says it accepts 18 data not 16 bit as per SAA7220. What about the extra 2 bits? or will the PCM1733 accept 16 bit data without problems, every thing sorted by the 16 bit I2S lines?




Quote:
The TDA1540 is not an I2S bus device.
OOPS - finger problem!


PS - whats a 6 sigma black belt?
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Old 3rd February 2006, 06:21 PM   #6
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Default Re: Re: Its the datasheets,.................

Quote:
Originally posted by poynton


Thats what I thought. I was wanting to replace the SAA7220 ( 4x filter ) and TDA1541 with the pcm1733 (8x filter). What worries me is the specs. for the PCM1733 says it accepts 18 data not 16 bit as per SAA7220. What about the extra 2 bits? or will the PCM1733 accept 16 bit data without problems, every thing sorted by the 16 bit I2S lines?

An 18 bit device will accept anything up to 18 bits. Unlike some other devices, the '1733 will not explicitly limit the I2S wordlength to 16 bits so the state of the last two bits will depend on the source of I2S data.
The SAA7210 extends the LSB such that if the LSB is Low the rest of the frame is low and vice versa. This will result in a dynamic 2 bit offset. You can get rid of this, the CS8420, with its input register fixed at 24bits in I2S mode, goes so far as to caution against having this offset in the datasheet, but in this case it will probably be insignificant.



Quote:

PS - whats a 6 sigma black belt?
A consultant/giver-of-seminars in TQM,DFM,DFT,ISO9000 and other assorted gobbledegook of much exalted guru status. Unfortunately more than a few couldn't tell a flat pack from a flap jack.
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Old 3rd February 2006, 06:29 PM   #7
poynton is offline poynton  United Kingdom
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Default Re: Re: Re: Its the datasheets,.................

Quote:
Originally posted by rfbrw

A consultant/giver-of-seminars in TQM,DFM,DFT,ISO9000 and other assorted gobbledegook of much exalted guru status. Unfortunately more than a few couldn't tell a flat pack from a flap jack.
Ah- why didn't you say a 22year old, MBA with no work experience and a shiny suit!!


OK, I'll give it a try !!!
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