STN-36

About hardware chip initialization

 issue number:

 date of issue:

 media:

 connection:

 Information distinction:

 importance:

 Attachment:

 Subject supplement:

Contents

■ Important and strict adherence

Be sure to observe the items and prohibited items that the manual explains that the operation is undefined. These indefinite behaviors and phenomena differ depending on the Sega Saturn compatible machine and the hardware version. Therefore, be sure to initialize each hardware chip on the application side.

■ Be careful

For VDP1, VDP2, and SCSP, the values set in the BOOT-ROM (logo display, multiplayer screen, etc.) remain set in the hardware chip, so the application uses these values as the default values. Be sure to initialize it without using it.

■ Caution example

● Example 1: Notes on ECD and PSD bits in polygon drawing commands

When specifying the polygon drawing command, specify a fixed value "1" for both the ECD and SPD bits (bit7, 6) of the drawing mode word (CMDPMOD). If "0" is specified, the operation is undefined.

reference:

"HARDWARE MANUAL / VDP1 User's Manual"
7.7 Polygon drawing command

● Example 2: Notes on the Clip bit in the drawing mode word of each drawing command

If you set the drawing mode word (CMDPMOD) Clip bit (bit10) to 1 to use user clipping, be sure to issue the user clipping coordinate setting command. If you do not set the coordinates, the value will be undefined.

reference:

"HARDWARE MANUAL / VDP1 User's Manual"
7.2 User clipping