SEGA SATURN DEVELOPER'S MANUAL

Chapter 9 Precautions Notes on using

are as follows.

● VDP1 in general

Rotation readout of the frame buffer is prohibited during normal, high-resolution, HDTV, and double-dense interlace.
Only the drawing frame buffer can be accessed from the CPU.

System register

DMA access to system registers is prohibited. Be sure to use word access.
Be sure to set the system register after turning on the power.
Be sure to set the unused bits of the system register to 0.
Be sure to set DIE = 0 when rotating the frame buffer. Rotation readout with double-dense interlace is prohibited.
Please note that an undefined surface is displayed for one frame immediately after changing the DIE bit.
When changing TVM bit, it is necessary to mask the frame buffer. When changing, one frame of undefined surface is displayed.
Please set FCM = 0 and FCT = 0 for double dense interlace. Field switching is possible only at 1/60 seconds.
Set the erase light area so that (upper left coordinate XA) <(lower right coordinate XC) and (upper left coordinate YA) ≤ (lower right coordinate YC).

Command

The local coordinates must be set after turning on the power.
The settable range of clipping coordinates is from (0, 0) to (1023, 511).
The clipping coordinate range is (upper left coordinate XA) ≤ (lower right coordinate XC) and (upper left coordinate YA) ≤ (lower right coordinate YC).
Set the appropriate value for clipping according to the screen mode set by the TVM bit.
The user clipping area must be set inside the system clipping area. It can be set on the same line.
The upper left coordinate of the system clipping area is fixed to (0, 0) by hardware.
Set unused bits in the word you are using to 0 in the command table.
Calls within a command subroutine (call, jump call, skip call) are prohibited.