SEGA SATURN DEVELOPER'S MANUAL

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6.2.3 Notes on file system

(1) Specifying the working selector

When reading file information, the CD block requires a working selector. Specify one selector to move directories and retain file information. At this time, at least one free sector is required. Sectors that have been used are erased after processing.

(2) Selector settings

When accessing a file, the file system makes the following settings for the selector.

(A) Specified aperture connection status

Aperture input connector: Connects to a CD device.
True output connector: Connects to the same numbered buffer section.
False output connector: Disconnect from other selectors.

(B) Aperture condition

Table 6.1 Set aperture conditions

Operation	Aperture
Directory move	-Set the aperture frame address range. -Enable the frame address range in aperture mode.
Preserve file information
Read file	-Set the aperture frame address range (FAD range). -Set the file number (FN) for the aperture subheader condition. -Enable FAD range and FN selection in aperture mode.

 Operation

 Aperture

 Directory move

-Set the aperture frame address range. 
-Enable the frame address range in aperture mode.

 Preserve file information

 Read file

-Set the aperture frame address range (FAD range). 
-Set the file number (FN) for the aperture subheader condition. 
-Enable FAD range and FN selection in aperture mode.

(3) CD playback range and drive command

When accessing a file, the playback range is the default value (from the beginning of the disc to the end).
∙ Drive commands (CD playback, pause, etc.) are executed as they are even during file system operation. Be careful as it can interfere with file system operations.
The settings (ECC count, retry count, etc.) set by CD block initialization (CDC_CdInit) are also valid when accessing files.
∙ Automatic pause / pause when the buffer is full works as usual.

(4) Termination and cancellation of file access

EFLS flag is set to 1 when file access is terminated or canceled. File access is canceled when the tray is open.
If the directory movement or file information retention is in progress, the file information table will be discarded (initialized) and no information will be entered if file access is canceled.

(5) For multi-session

The file system refers to the volume descriptor of the last session.

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