CD drive
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
FO - Focus Offset (Max value 100kΩ +/- 10%)
Measured resistance: 12 kΩ
- 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 (Max value 4,7kΩ +/- 10%)
Measured resistance: 1,25 kΩ
- Controls the sensitivity of the autofocus system
- Determines the speed of focus correction
- Effect: Focus responsiveness to distance variations
TB - Tracking Balance (Max value 100kΩ +/- 10%)
Measured resistance: 46 kΩ
- Adjusts the center position of the track following system
- Compensates for mechanical alignment defects
- Effect: Laser centering on the track
TG - Tracking Gain (Max value 4,7kΩ +/- 10%)
Measured resistance: 1,8 kΩ
- Controls the sensitivity of track following
- Determines the strength of lateral correction
- Effect: Track following responsiveness to track deviations
TO - Tracking Offset (Max value 100kΩ +/- 10%)
Measured resistance: 49 kΩ
- Adjusts the resting position of the tracking system
- Compensates for mechanical drift
- Effect: Initial lateral laser position
In the following image, here are the two points where resistance measurements should be taken.
Big thanks to Domkid for letting me borrow his Neo CD!
Capacitor values
PCB CD Controller Type NO.4 F3801AF
| Capa # | Type | Value | Voltage |
| C101 | POLARISED | 47 uF | 16V |
| C102 | POLARISED | 47 uF | 16V |
| C108 | SMD 0805 | 100 nF | |
| C109 | SMD 0805 | 100 nF | |
| C110 | SMD 0805 | 100 nF | |
| C112 | SMD 0805 | 35 nF | |
| C113 | POLARISED | 330 uF | 16V |
| C114 | POLARISED | 100 uF | 16V |
| C116 | SMD 0805 | 100 nF | |
| C117 | SMD 0805 | 100 nF | |
| C118 | SMD 0805 | 35 nF | |
| C119 | SMD 0805 | 25 nF | |
| C124 | POLARISED | 100 uF | 16V |
| C125 | SMD 0805 | 35 nF | |
| C127 | POLARISED | 4,7 uF | 16V |
| C128 | SMD 0805 | 100 nF | |
| C131 | SMD 0805 | 100 nF | |
| C132 | POLARISED | 1 uF | 50V |
| C133 | POLARISED | 47 uF | 16V |
| C134 | POLARISED | 33 uF | 25V |
| C137 | SMD 0805 | 100 nF | |
| C141 | SMD 0805 | 100 nF | |
| C143 | POLARISED | 0,47 uF | 50V |
| C144 | SMD 0805 | 1,5 nF | |
| C145 | SMD 0805 | 1,5 nF | |
| C146 | SMD 0805 | 100 nF | |
| C149 | SMD 0805 | 60 nF | |
| C154 | SMD 0805 | 35 nF | |
| C155 | POLARISED | 100 uF | 16V |
| C159 | SMD 0805 | 60 nF | |
| C161 | POLARISED | 100 uF | 16V |
| C166 | POLARISED | 100 uF | 16V |
| C167 | SMD 0805 | 12 pF | |
| C168 | SMD 0805 | 4 pF | |
| C170 | SMD 0805 | 1 uF | |
| C171 | SMD 0805 | 1 uF | |
| C180 | SMD 0805 | 100 nF | |
| C181 | SMD 0805 | 100 nF | |
| C182 | SMD 0805 | 100 nF |
- Big thanks to Domkid for letting me borrow his Neo CD!