CD drive: Difference between revisions

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[[File:Cd2_cdboard1.jpg|thumb|right|CD2 CD drive board.]]
[[File:Cd2_cdboard1.jpg|thumb|right|Top-loading drive control board.]]


Or "CD drive". The part that fails before everything else in [[CD systems]]. Also see [[optical pickups]].
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 pickups|optical pickup]].


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


It is made of:
The control board has:
* A 4-bit maskROM MCU (Sony CXP5084), taking care of sequencing and communication (command execution and status report).
* 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 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 servo controler (Sony CXA1372) to drive the pickup coils for tracking and focus.
* A spindle and sled motor driver (Rohm BA6396).
* A spindle, sled (and tray) motor driver.


==Connections==
=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 and a logic analyzer.
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):
Connector pinout, directions are from CDD (CD Drive) to CDC (CD Controller):
Line 28: Line 32:
| Clock
| Clock
| Output
| Output
| Tells the CDC when to change HOCK
| Communication clock to CDC
|-
|-
| 2
| 2
Line 52: Line 56:
| Clock
| Clock
| Input
| Input
| Tells the CDD data is ready on D0~3
| Communication clock from CDC
|-
|-
| 6
| 6
Line 58: Line 62:
| rowspan="4" | Data
| rowspan="4" | Data
| rowspan="4" | Both
| rowspan="4" | Both
| rowspan="4" | 4-bit data bus
| rowspan="4" | 4-bit command/status data bus
|-
|-
| 7
| 7
Line 76: Line 80:
| Clock
| Clock
| Output
| Output
| I2S bit clock, should be 44100 * 32 = 1.4112MHz
| Serial bit clock, should be 44100 * 32 = 1.4112MHz
|-
|-
| 12
| 12
Line 82: Line 86:
| Data
| Data
| Output
| Output
| I2S data
| Serial data
|-
|-
| 13
| 13
Line 91: Line 95:
|-
|-
| 14
| 14
| MUTE?
| D/M ?
| Signal
| Signal
| Input
| Output
| Put low to gate SDATA ?
| Data/Music. Low during music playback ?
|-
|-
| 15
| 15
Line 121: Line 125:
|}
|}


Some signal has to be "D/M", an output which indicates if SDATA is audio or data. There's a /RESET somewhere also.
Missing: /RESET, C2PO, and 16MHz.


==Communication==
==Front-loading model==


{{Chipname|NEO-MGA}} takes care of the I/Os through registers {{Reg|REG_CDDCTRL}}, {{Reg|REG_CDDINPUT}}, {{Reg|REG_CDDOUTPUT}}.
Connector pinout, directions are from CDD (CD Drive) to CDC (CD Controller):


[[File:Cdunit4bit.png]]
{| class="regdef"
 
|'''Pin #'''
* The CDD regularly sends a low pulse on its /IRQ output to initiate a data exchange.
|'''Name'''
* HOCK goes low, indicating that the CDC aknowledges the request. The 4-bit bus direction is CDD to CDC.
|'''Type'''
* CDCK goes low, indicating that the CDD is starting to send its status data (green A). Diagram fix: A should be ready on CDCK low.
|'''Direction'''
* HOCK goes high and the CDC reads the status data (A).
|'''Description'''
* CDCK goes returns high.
|-
* HOCK goes returns high.
| 1
* CDCK goes low, the B word is ready.
| SGND
* The cycle continues on for 10 words.
| Power
 
| -
(The delay here is not necessary, but it can be seen on the NeoGeo CD and is caused by the [[system ROM]] program preparing stuff).
| Ground
 
|-
* HOCK goes low and the 4-bit bus direction is inverted (CDC to CDD). The command data is set (red A).
| 2
* CDCK goes low, indicating that the CDD has read the data (A).
| SVCC
* HOCK returns high.
| Power
* CDCK returns high.
| -
* HOCK goes low, the B word is ready.
|
* The cycle continues on for 10 words.
|-
 
| 3
===Status data (green)===
| VCC
 
| Power
* A: Status
| -
* B: Status
|
* C: Minutes high digit
|-
* D: Minutes low digit
| 4
* E: Seconds high digit
| WFCK
* F: Seconds low digit
| Clock
* G: Frames high digit
| Output
* H: Frames low digit
| Write Frame Clock
* I: Extension
|-
* J: Checksum (see below)
| 5
 
| GND
===Command data (red)===
| Power
 
| -
* A: Command
| Ground
* B~H: Depends on command
|-
* I: Checksum (see below)
| 6
 
| SCOR
===Checksum===
| Pulse
 
| Output
The checksum digit is the sum of all 9 previous digits, + 5, XOR 15, modulo 15: ((sum + 5) ^ 0xF) & 0xF.
| Subcode sync
 
|-
==Commands==
| 7
 
| MUTE
===0: STATUS===
| ?
No parameters.
|
 
|
===1: STOP ALL===
|-
No parameters. Stops CDDA playback, disk spin, and sets drive in data mode.
| 8
 
| SBSO
===2: TOC COMMAND===
| Data
D: Command code:
| Output
 
| Subcode data
====0: GET POSITION====
|-
MSF in status will be the current position from the beginning of the CD (absolute).
| 9
====1: GET TRACK POSITION====
| EXCK
MSF in status will be the current position from the beginning of the track (relative).
| Clock
====2: GET TRACK NUMBER====
| Input
Minutes in status will be the current track.
| Subcode clock
====3: GET CD LENGTH====
|-
MSF in status will be the total CD length.
| 10
====4: GET FIRST AND LAST TRACKS====
| EMP
Minutes in status will be the first track (normally 1), seconds will be the last.
| ?
====5: GET TRACK NUMBER====
| ?
MSF in status will be the start of the desired track. If the track is a data track, the frames high digit's fourth bit will be 1 (OR 8).
| EMPty ?
 
|-
===3: PLAY===
| 11
* B: Minutes high digit
| DOUT
* C: Minutes low digit
| Data
* D: Seconds high digit
| Output
* E: Seconds low digit
| ?
* F: Frames high digit
|-
* G: Frames low digit
| 12
 
| 6MHz
Starts playing audio.
| Clock
 
| ?
===4: SEEK===
| ?
* B: Minutes high digit
|-
* C: Minutes low digit
| 13
* D: Seconds high digit
| LRCK
* E: Seconds low digit
| Clock
* F: Frames high digit
| Output
* G: Frames low digit
| DATA L or R channel (44100Hz)
 
|-
Sets pickup at desired position.
| 14
 
| DATA
===6: PAUSE===
| Data
Pauses CDDA playback (disk keeps spinning).
| ?
 
| Data stream
===7: RESUME===
|-
Resumes CDDA playback.
| 15
 
| BCLK
===8: FAST-FORWARD===
| Clock
Unknown.
| Output
 
| DATA bit clock (44100 * 24 * 2 = 2.12MHz)
===9: REWIND===
|-
Unknown.
| 16
 
| C2PO
===10: INIT===
| Data
Sets pickup at lead-in ?
| Output
 
| Error flag
===12: CLOSE===
|-
Closes the tray on the front-loading NeoGeo CD.
| 17
 
| rowspan="4" | DB0~3
===13: OPEN===
| rowspan="4" | Data
Opens the tray.
| rowspan="4" | Both
| rowspan="4" | 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
|}


==Adjustments==
==Adjustment pots==


To do !
To do !


[[Category:Chips]]
[[Category:Chips]]
[[Category:Repairs]]
[[Category:CD systems]]
[[Category:CD systems]]

Latest revision as of 18:48, 22 June 2019

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 !

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