The function of each bit is as follows.
Bit 2: HDTV valid bit
0 = NTSC, PAL
1 = HDTV, 31KC
Bit 1: Frame buffer rotation enable bit
0 = non-rotation
1 = Rotation
Bit 0: Bit width selection bit
0 = 16bit / pixel
1 = 8bit / pixel 
 

Table 4.2 Screen Mode

 Normal 
 (NTSC, PAL)  

 High Res 
 (NTSC, PAL 
 High Res)  

 Rotation 16 
 (NTSC, PAL 
 Rotation)  

 Rotation 8 
 (NTSC, PAL 
 Rotation)  

 HDTV 
 (31KC, HDTV)  

TVM			Screen mode		bit width	frame buffer screen size	inter Race	VDP CLK (MHz)
bit 2	1	0	Name	Resolution				NTSC	PAL
0	0	0	320 × 224 320 × 240 352 × 224 352 × 240	16bit / pixel	512 horizontal × vertical 256	Yes	26.8426 26.8426 28.6364 28.6364	26.6564 26.6564 28.4375 28.4375
0	0	1	640 × 224 640 × 240 704 × 224 704 × 240	8bit / pixel	Width 1024 × Vertical 256	Yes	26.8426 26.8426 28.6364 28.6364	26.6564 26.6564 28.4375 28.4375
0	1	0	320 × 224 320 × 240 352 × 224 352 × 240	16bit / pixel	512 × Vertical 256	Single-dense Yes	26.8426 26.8426 28.6364 28.6364	26.6564 26.6564 28.4375 28.4375
0	1	1	320 × 224 320 × 240 352 × 224 352 × 240	8bit / pixel	512 × Vertical 512	Single density only Yes	26.8426 26.8426 28.6364 28.6364	26.6564 26.6564 28.4375 28.4375
1	0	0	320 × 240 352 × 240	16bit / pixel	512 × vertical 256	prohibited	26.8426 28.6364	26.6564 28.4375
Other than the above			Prohibit setting (do not set)