CD drive commands

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)						?	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)