Outputformat Sony CXD2500 Chip

joe

Member
2001-10-23 8:44 pm
Hamburg
Hi, my CDP has a Sony CXD2500 Chip for the signal processing in the transport. I would like to use the signal from it to feed a external DAC, ASRC, digital Transmitter or whatever. In the Datasheet the serial outputformat is called "48bit, 2´s complements, MSB first" which confuses me. Is this a stereo 24bit Signal or is it a special sony format? Is this signal compatible with the standard digital filters like e.g. DF1704? Never saw a 48bit signal for any other chip.

joe
 
I have not looked at this decoder's data sheet, but I have worked with several other decoders from the same family. The output is 16 bit stereo, right justified. It will go into most digital filter ICs or integrated filter DACs, provided you set them to 16 bit "standard", "Japanese" or "Sony" format. The rest of the 48 or 64 bit frames are just stuffed with zeroes. As Sony is a right-justified format, you need to know how many relevant bits there are. In a CD-player, it has to be 16.

Note that some of the more modern DACs such as the AD1853 have I2S as the default format and no longer provide mode pins, so you will need a controller to set the correct format or install some glue logic.

On most CXD decoders, the SPDIF can be inactivated by software but in the players without a digital output that I have checked so far, this was never the case. But then you'd have to include a receiver chip which might only make sense if you want to avoid the glue logic. Also, it would degrade the timing unless you insert a master clock that sits on the DAC board and clocks the DAC directly.



Eric
 

rfbrw

Member
2001-10-26 11:51 pm
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One cannot be so cavalier and say set it to 16 bits and away you go. Whether the frame is stuffed with zeros or sign-extended does not preclude the need to select the correct frame size. Dacs that work with 48 bit L/R frames are as rare as rocking-horse droppings. The trend in a lot of literature I have seen is to refer to 48 bit frames as the Sony format and 64bit frames as the Sony/BurrBrown format though this is by no means a hard and fast rule making things even more confusing.

ray
 
CXD2500 Output Format

Hi Alll,
I happen to own a Sony CDP with the mentioned chip.
The L/R clock is 44.1 kHz.
During L/R is high there is room for 24 bits; only 16 bits are used. My scope tells me the rest are zero's.
This means that the bitclock is 48x44.1kHz= 2.1168 MHz. Please note that this format is used to feed the Sony CXD1244 digital filter internally.

The SPDIF output (pin 60) adheres to the standard used for that format. Here is room for 32 bits; again only 16 bits used.

So if you want to connect the DF1704 filter directly to the Sony CXD2500 chip the datasheet of BB claims:
"BCKIN can run at 32fs, 48fs , or 64 fs. LRCIN is run at the fs rate. Fig 4 shows the input data formats.". I believe it would work without any problem.

If you wish to use the DF1704 in a separate DAC component you can use the CS8412 or 8414 digital input receiver. See for example the scheme in
http://www.diyaudio.com/forums/showthread.php?s=&postid=44053#post44053

Hope this helps;)