CD drive commands

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These command formats probably also apply to other CD-ROM drives of the era, like the Sega CD's one.

All nibble values are in hex.

Command 0: STATUS

No parameters. No operation. May be used to just read the status.

Send:

Nibble 0 1 2 3 4 5 6 7 8 9
Value 0 0 0 0 0 0 0 0 0 Checksum (A)

Command 1: STOP ALL

No parameters. Stops disk, laser, and sets drive in data mode.

Send:

Nibble 0 1 2 3 4 5 6 7 8 9
Value 1 0 0 0 0 0 0 0 0 Checksum (9)

Command 2: TOC COMMAND

Nibble D is the sub-command code:

Sub-command 0: GET POSITION

MSF in status will be the current position from the beginning of the CD (absolute).

Send:

Nibble 0 1 2 3 4 5 6 7 8 9
Value 2 0 0 0 0 0 0 0 0 Checksum (8)

Get:

Nibble 0 1 2 3 4 5 6 7 8 9
Value ? 0 Current absolute MSF position 0 Checksum

Sub-command 1: GET TRACK POSITION

MSF in status will be the current position from the beginning of the track (relative).

Send:

Nibble 0 1 2 3 4 5 6 7 8 9
Value 2 0 0 1 0 0 0 0 0 Checksum (7)

Get:

Nibble 0 1 2 3 4 5 6 7 8 9
Value ? 1 MSF position in current track 0 Checksum

Sub-command 2: GET TRACK NUMBER

Minutes in status will be the current track.

Send:

Nibble 0 1 2 3 4 5 6 7 8 9
Value 2 0 0 2 0 0 0 0 0 Checksum (6)

Get:

Nibble 0 1 2 3 4 5 6 7 8 9
Value ? 2 Current track number 0 0 0 0 0 Checksum

Sub-command 3: GET CD LENGTH

MSF in status will be the total CD length.

Send:

Nibble 0 1 2 3 4 5 6 7 8 9
Value 2 0 0 3 0 0 0 0 0 Checksum (5)

Get:

Nibble 0 1 2 3 4 5 6 7 8 9
Value ? 2 CD length in MSF 0 Checksum

Sub-command 4: GET FIRST AND LAST TRACKS

Minutes in status will be the first track (normally 1), seconds will be the last.

Send:

Nibble 0 1 2 3 4 5 6 7 8 9
Value 2 0 0 4 0 0 0 0 0 Checksum (4)

Get:

Nibble 0 1 2 3 4 5 6 7 8 9
Value ? 4 First track number Last track number 0 0 0 Checksum

Sub-command 5: GET TRACK MSF

MSF in status will be the start of the desired track (nibbles E and F). If the track is a data track, the frames upper digit's 4th bit will be 1.

Send:

Nibble 0 1 2 3 4 5 6 7 8 9
Value 2 0 0 5 Desired track number 0 0 0 Checksum

Get:

Nibble 0 1 2 3 4 5 6 7 8 9
Value ? 5 MSF of track start (see note above) Lower digit of track # Checksum

Sub-command 6: GET ERROR

Unused ? Returns the last error code.

Command 3: PLAY

Starts playing from specified MSF.

Send:

Nibble 0 1 2 3 4 5 6 7 8 9
Value 3 0 Start MSF 0 Checksum

Command 4: SEEK

Moves pickup to specified MSF.

Send:

Nibble 0 1 2 3 4 5 6 7 8 9
Value 4 0 Seek MSF 0 Checksum

Command 6: PAUSE

Pauses CDDA playback (disk keeps spinning).

Send:

Nibble 0 1 2 3 4 5 6 7 8 9
Value 6 0 0 0 0 0 0 0 0 Checksum (4)

Command 7: RESUME

Resumes CDDA playback after pause.

Send:

Nibble 0 1 2 3 4 5 6 7 8 9
Value 7 0 0 0 0 0 0 0 0 Checksum (3)

Command 8: FAST-FORWARD

No parameters needed ?

Command 9: REWIND

No parameters needed ?

Command 10: INIT

Seeks to CD lead-in ?

Command 11: Unknown

Used but unknown behavior. "Access to the top of the specified tracK obtained the BCD code on the second byte."

Command 12: CLOSE

Closes the tray on the front-loading NeoGeo CD.

Send:

Nibble 0 1 2 3 4 5 6 7 8 9
Value 12 0 0 0 0 0 0 0 0 Checksum (E)

Command 13: OPEN

Opens the tray.

Send:

Nibble 0 1 2 3 4 5 6 7 8 9
Value 13 0 0 0 0 0 0 0 0 Checksum (D)