Chapter 9 Precautions for use

The precautions for use are as follows.

● VDP1 in general

• Rotational reading of the frame buffer is prohibited during normal, high resolution, HDTV, and double-dense interlacing. [ Reference ]

• The CPU can only access the drawing framebuffer. [ Reference ]

● System registers

• DMA access to system registers is prohibited. Be sure to use word access. [ Reference ]

• Be sure to set the system register after turning on the power. [ Reference ]

• Be sure to set the unused bits of the system register to 0. [ Reference ]

• Be sure to set DIE = 0 when reading the frame buffer by rotation. Rotational reading with double-dense interlace is prohibited. [ Reference ]

• Note that an irregular surface is displayed for one frame immediately after changing the DIE bit. [ Reference ]

• When changing the TVM bit, it is necessary to mask the frame buffer. When changing, one frame of irregular surface is displayed. [ Reference ]

• For double-dense interlacing, set FCM = 0 and FCT = 0. Field switching is possible only at 1/60 second. [ Reference ]

• Set the erase light area so that (upper left coordinate XA) <(lower right coordinate XC) and (upper left coordinate YA) ≤ (lower right coordinate YC). [ Reference ]

● Command

• Relative coordinates need to be set after the power is turned on. [ Reference ]

• The clipping coordinate can be set from (0,0) to (1023,511). [ Reference ]

• The range of clipping coordinates is (upper left coordinate XA) ≤ (lower right coordinate XC) and (upper left coordinate YA) ≤ (lower right coordinate YC). [ Reference ]

• For clipping, set the appropriate value for each screen mode set by the TVM bit. [ Reference ]

• Be sure to set the user clipping area inside the system clipping area. It can be set on the same line. [ Reference ]

• The upper left coordinate of the system clipping area is fixed at (0,0) in hardware. [ Reference ]

• In the command table, set the unused bits in the word you are using to 0. [ Reference ]

• Calls (call, jump call, skip call) in the command subroutine are prohibited. [ Reference ]

• Returns (return, jump return, skip return) in the command main routine are prohibited. [ Reference ]

• Only 0H, 5H, 6H, 7H, 9H, AH (10), BH (11), DH (13), EH (14), and FH (15) are available as zoom point values. Other settings are prohibited. [ Reference ]

• In the state of HSS = 1, the end code of the original picture is ignored regardless of whether the sprite is enlarged or reduced. [ Reference ]

• Set the lower 2 bits of CMDLINK to 00. [ Reference ]

• Set the lower 2 bits of the lookup table to 00. [ Reference ]

• When setting the color bank, set 0000 for the lower 4 bits of the color bank data. [ Reference ]

• For non-texture, set ECD = 1, SPD = 1, and color mode = 0. [ Reference ]

• When performing color calculation with non-texture, set RGB data (8000H or more) to non-texture color. [ Reference ]

• When setting to RGB mode and using 7FFFH data for the original picture, set ECD = 0. [ Reference ]

• When setting to RGB mode and using 0000H data for the original picture, set SPD = 0. [ Reference ]

• When set to RGB mode, setting the framebuffer to 8 bits / pixel is prohibited. Modes 0, 1, 2, 3, and 4 are the only color modes that can be 8-bit / pixel. [ Reference ]

• When the frame buffer is set to 8 bits / pixel, set the color calculation mode to 0. Only replacement is possible. Other color operations are prohibited. [ Reference ]

• When the framebuffer is set to 8 bits / pixel, the top 8 bits of the non-textured color are ignored. At this time, the use of RGB data is prohibited. [ Reference ]

• Do not set the MSB on-bit (MON) to 1 when the framebuffer is set to 8 bits / pixel. [ Reference ]

• When the MSB on-bit (MON) is set to 1, the color calculation mode should be set to 0. [ Reference ]

• Store the command table at address 000000H of VRAM. [ Reference ]