Technical information

SEGA Confidential

SATURN Virtual CD System User's Manual

Section I: VCD I/F Board Main Functions

The VCD I/F Board (RT-V1A) is an ISA expansion board for PC-compatible ma-

chines that handles transfers of commands and messages between PC-compatible

computers and the CD Block (RT-V1B) within a target box, sends CD-ROM data

from PC-compatible machines to the CD Block, and transfers CDDA data and other

types of CD-ROM data.

1.0 Main Functions

• Communicating with the CD Block

Receives commands from the CD Block, performs the appropriate processing,

and returns status data to the CD Block.

• Communicating with PC-compatibles

Fetches commands required by the PC-compatible from commands in the CD

Block and sends them. The PC in turn returns the data required by these com-

mands.

• Receiving Data from the PC

When a Play command is sent to the PC, the PC prepares CD-ROM data, CDDA

data or, if necessary, R~W subcode data. The VCD I/F Board receives this data

via the on-board DMA controller.

• Sending data to the CD Block

Scramble processing is preformed on the data from the PC, and the data is then

converted into serial data. This serial data is sent to the CD Block.

2.0 Data Transfer Speed

Two transfer speeds, normal speed and double speed, can be set for CD-ROM data

transfers. The transfer speed is set by commands sent from the CD Block.