Display Window
V-POS
44 ($29)
H-POS
129 ($81)
The starting position is always interpretted in low-res mode, and doesn't change with hi-res or interlaced.
Calculated DIWSTRT
$2C81
HEIGHT
256 lines
WIDTH
320 px
Similar to DIWSTRT, the stopping position is always interpretted in low-res mode, and doesn't change with hi-res or interlaced.
Calculated DIWSTOP
$2CC1
DMA Data Fetch
$38
$D0
COPIED!
The idea is to figure out, how many 16-bit words of data the HW needs to fetch to fill the width of the display window.
312
lines
lines
~226 ccs
(0,0)
SYNC START
SYNC START
Standard ($81,$2C)
VISIBLE
VISIBLE
Deadzone
Deadzone
Overscan
Overscan
Blanking
Window
Fetch
- HW resolution of display window start/stop is twice the HW resolution of data fetch.
- 1 Color Clock = 2 low-res pixels / 4 hi-res pixel
System Status
VALIDDMA Fetch logic is synchronized with Display Window.