CD drive

File:Cd2 cdboard1.jpg

Top-loading drive control board.

The part that makes you wait and fails in CD systems. The ones used in the NeoGeo consoles are very similar to those found in the Sega CD. They're basically enhanced audio CD drives, which are also able to read CD-ROM data tracks.

Made of a control board and an optical pickup.

The NeoGeo CD top-loading model drive was made by Sony. The CDZ one was made by Sharp ?

The control board has:

• A 4-bit mask ROM MCU (Sony CXP5084), taking care of operation sequencing and communication with the NeoGeo.
• A DSP (Sony CXD2500) to process analog data from the pickup.
• A servo controler (Sony CXA1372) to drive the pickup coils for tracking and focus.
• A spindle, sled (and tray) motor driver.

Connections

Some say the protocol was standard for the time, but clear information is hard to find. This was guessed from the system ROM disassembly, Sega CD documents and a logic analyzer.

Top-loading model

Connector pinout, directions are from CDD (CD Drive) to CDC (CD Controller):

Pin #	Name	Type	Direction	Description
1	CDCK	Clock	Output	Communication clock to CDC
2	?	?	?	High ?
3	/IRQ	Signal	Output	Asks the CDC for a data exchange (low pulse at ~64Hz)
4	?	?	?	High ?
5	HOCK	Clock	Input	Communication clock from CDC
6	D0~3	Data	Both	4-bit command/status data bus
7
8
9
10	?	?	?	?
11	BCLK?	Clock	Output	Serial bit clock, should be 44100 * 32 = 1.4112MHz
12	SDATA	Data	Output	Serial data
13	LRCK	Signal	Output	I2S word clock, should be 44100Hz. Audio L/R switch for the DAC.
14	D/M ?	Signal	Output	Data/Music. Low during music playback ?
15	GND	Power	-	Ground
16	5V	Power	-	+5V for logic
17	9V	Power	-	+9V for motors and coils
18	GND	Power	-	Ground

Missing: /RESET, C2PO, and 16MHz.

Front-loading model

Connector pinout, directions are from CDD (CD Drive) to CDC (CD Controller):

Pin #	Name	Type	Direction	Description
1	SGND	Power	-	Ground
2	SVCC	Power	-
3	VCC	Power	-
4	WFCK	Clock	Output	Write Frame Clock
5	GND	Power	-	Ground
6	SCOR	Pulse	Output	Subcode sync
7	MUTE	?
8	SBSO	Data	Output	Subcode data
9	EXCK	Clock	Input	Subcode clock
10	EMP	?	?	EMPty ?
11	DOUT	Data	Output	?
12	6MHz	Clock	?	?
13	LRCK	Clock	Output	DATA L or R channel (44100Hz)
14	DATA	Data	?	Data stream
15	BCLK	Clock	Output	DATA bit clock (44100 * 24 * 2 = 2.12MHz)
16	C2PO	Data	Output	Error flag
17	DB0~3	Data	Both	4-bit command/status data bus
18
19
20
21	HOCK	Clock	Input	Communication clock from CDC
22	RESET	Pulse	Input	The name says it all
23	/IRQ	Signal	Output	Asks the CDC for a data exchange
24	L-MUTE	?
25	CDCK	Clock	Output	Communication clock to CDC

Adjustment pots

To do ! Adjust values

FO - Focus Offset

• Adjusts the resting position of the focusing lens
• Compensates for mechanical variations in the optical system
• Effect: Initial laser position relative to CD surface

FG - Focus Gain

• Controls the sensitivity of the autofocus system
• Determines the speed of focus correction
• Effect: Focus responsiveness to distance variations

TB - Tracking Balance

• Adjusts the center position of the track following system
• Compensates for mechanical alignment defects
• Effect: Laser centering on the track

TG - Tracking Gain

• Controls the sensitivity of track following
• Determines the strength of lateral correction
• Effect: Track following responsiveness to track deviations

TO - Tracking Offset

• Adjusts the resting position of the tracking system
• Compensates for mechanical drift
• Effect: Initial lateral laser position

Capacitor values

PCB Type NO.4 F3801AF

Capa #	Type	Value	Voltage
C108	SMD
C109	SMD
C110	SMD
C112	SMD	35 nF
C114	POLARISED	100 uF	16V
C116	SMD	105 nF
C117	SMD	105 nF
C118	SMD	35 nF
C119	SMD	25 nF
C124	POLARISED	100 uF	16V
C125	SMD	35 nF