RRD50 interface

cctech at vax-11.org wrote: The RRD50 is a Philips/LMSI CM100 CD-ROM drive, which was based on the Philips CD100 CD player. There was a CM155 host adapters for PCs. I used to have the CM100 and CM155 service manuals, but don't have them readily available now. This site claims to sell a PDF of the CM100 service manual for $29: http://www.manuals-in-pdf.com/index.php?main_page=product_info&products… However, it might be a manual for the Philips CM100 Transmission Electron Microscope, rather than the Philips CM100 CD-ROM drive. It would have been nice if Philips hadn't used the same model number for two entirely different products. The CM100 interface is not I2S; there are I2S or similar signals inside the drive, but there's a bunch of logic that reformats the data for the interface. The interface uses EIA-422 differential pairs. IIRC there were one or two pairs for the data, one for commands to the 8051 microcontroller, and one for status back from the 8051. The drive hardware does not perform the C3 error correction; that is up to the host adapter or the host. The CM155 is a very dumb adapter, so the driver must do the C3 error correction. I spent some time reverse-engineering the 8051 firmware, though truth be told, there isn't really much of interest in there. Oddly enough, they came very close to implementing the CM100 interface in such a way that multiple drives could be used on one host adapter, by assigning them unit numbers on the DIP switch, but they didn't put in the EIA-485 drivers that would be necessary to make it work. (EIA-422 does not define drivers with a high-impedance state, while EIA-485 does.) The CM100 uses the Signetics SAA7000 series CD-Audio chipset, since Signetics was owned by Philips. There was a CM110 which had an additional board that adapted the CM100 interface to SCSI. I'd like to find one of those, or the M7552 (KRQ50) or M7490 host adapters for the RRD50, but I haven't ever found them. Eric