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cddriver.md

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CD-DRIVER

CD Driver - special chip for controlling CD-ROM motors and coils:

  • Spindel - The main motor on which the disk rotates. Usually spins in one direction.
  • Sledge - The carriage carries the laser head. The carriage is usually driven by a worm gear.
  • Focusing coil - Moves the laser diode perpendicular to the disk surface
  • Tracking coil - designed to move the laser beam precisely over the tracks of the CD

A very good summary of CD design is available here: http://www.radiofan.ru/faq/cd/part1.htm

Older revisions of motherboards had the CD Driver represented by a ROHM chip (IC704) and a bunch of third party chips. In later revisions the CD Driver was replaced by a single common chip IC722. That's what we will take it as a "reference".

IC704

Ba6392fp_sm

Full resolution: https://drive.google.com/file/d/1tPvfsoNfepg7JGQX0SbOree_kSWo4pOS/view

Hardware Interface

IC722_overview

The motors and coils are controlled by CD-DSP:

  • TFDR/TRDR: Tracking coil control (F-forward, R-reverse)
  • FFDR/FRDR: control of the focus coil
  • SRDR/SFDR: motor carriage control
  • MDP: motor dirve phase: control the speed of the disc, by giving special pulses

It is possible to set the speed of the disc (1x/2x), by giving the SPEED signal, which comes from SUB-CPU

The MUTE signal is connected to the RESET3.3 signal (resetting the low voltage circuits of the PSX subsystem).

Forward/Reverse

TBD.

MDP

There is a description of the MDP signal in the CD-DSP documentation.

MDP

The motor can be controlled in two modes (set in the CD-DSP DCLV PWM MD settings): with and without the MDS.

In particular IC722 is controlled by a single MDP pin (without MDS involvement), and the positive polarity sets the motor acceleration and the negative polarity sets the motor deceleration. The acceleration value is coded by PWM and n varies from 0 to 31.