7 Sep
2010
7 Sep
'10
11:01 a.m.
Sorry for the mis-threading, I lost the original posting.
The older CDROM drives were in fact CD audio drives with the logic bolted
on in place of the serial DACs. In fact I used to have an old Reference
I have (and still use) an ancient external Philips single-speed CD-ROM
drive (CDD462) which is a modified (by Philips) CD player. To the exptent
that you need both its service manual and the one for the CR player it
was based on to repair it.
In fact for the one fault I've had with it, the CD-ROM drive service
manual was not a lot of help. The mains switch failed. Yes, it's shown on
the schematics, but for some reason not listed in the parts list. It is
listed in the CD player manual, so I could order a replacement.
IIRC, there is a ULA-type thing conencted to the input of the DACs which
extracts the right bit of the bit-stream and sends it to the interface
card in the PC (one ASIC and a buffer RAM). There's also a serial
command/status link from the PC to the control microcontroller in the
CD-ROM drive, to let the PC select the block to start reading from, etc.
The main CD-player chipset was still there, it was the Philips one, of
course, as docuemtned in their data books.
Technology drive which was a commercial CD drive and
several boards worth
of discrete logic which performed the C3 ECC correction. The CDROM
That sounds like fun...
functionality was just connected in place of the DACs.
The Philis unit I mentioned kept the DACs, and even the headphone
amplifdier. It ahs the normal play/stop/prev/next buttons on the front,
and can be used as a CD-player without having a computer conencted.
I suspect the RRD50 interface is three main wires:
Bit clock (32x data rate)
Left/Right (high for left, low for right, or vice versa)
Serial data
And, if memory serves it was called an I2S interface, though what the
acronym stands for I don't recall.
I2S = Inter IC Sound (at least in this case [1]). There's also the
totally different, but also from Philips I2C (Inter IC Communication)
[1] Long before this there was an American company called IIS or I2S
(I've seen both) standing for International Imaging Systems or something
like that. They made some very nice image processor/display units for
PDP11s
-tony