<14/54> VDP1 User's Manual / 4.3 Plot Trigger Register

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VDP1 User's Manual / Chapter 4 System Registers

■ 4.3 Plot trigger register

The Plot trigger mode register (PTMR) controls the start of drawing. This is a write-only 16-bit register located at address 100004H. After powering on or resetting, the value will be reset to 00B. Fix unused bits to 0.

PTMR 100004H (R) bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 PTM

Plot trigger mode: plot trigger mode (PT), bit0,1

Controls the start of drawing. When the plot trigger mode is 10B, drawing starts automatically at the same time as the frame starts. If the plot trigger mode is set to 01B, drawing will start when the register is written. If 01B is written to the plot trigger mode during drawing, drawing will start from the beginning of the command table at that point. When the plot trigger mode is 00B, drawing does not start even if the frame starts. It will be idling. After powering on or resetting, the value will be reset to 00B.

PTMR 100004H (R)	bit15	bit14	bit13	bit12	bit11	bit10	bit9	bit8	bit7	bit6	bit5	bit4	bit3	bit2	bit1	bit0
0	0	0	0	0	0	0	0	0	0	0	0	0	0	PTM

PTM		Drawing mode
Bit 1	0	Drawing mode
0	0	Idle by switching frames
0	1	Drawing starts when 01B is written
1	0	Automatically start drawing by switching frames
1	1	Setting prohibited (Please do not set)

When the plot trigger mode is rewritten from 01B to 00B or 10B, it becomes effective from the next frame buffer switching timing. However, when the plot trigger mode is rewritten from 00B or 10B to 01B, it becomes effective at that point and starts drawing even after automatic drawing by 10B. If the table is not rewritten, the same drawing will be performed, so the result of translucent color calculation will change. If you want to change only the drawing start mode without drawing, do as follows. Change the plot trigger mode from 10B to 00B. At the next frame, change the plot trigger mode from 00B to 01B.

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