Hi,
I would like to ask a question on LCD_OE signal in DM6437's VPBE.
In the figure above, LCD_OE has been configured as high active, and LCD screen has horizontal width 400, which is also the value of HINT.
|
row 2→row 1 |
HSTART 50→300: no effect on LCD_OE |
|
row 2→row 3 |
HVALID 180→90: LCD_OE high time to ½. |
|
row 2→row 4 |
HVALID 180→45: LCD_OE high time to ¼. |
The comparison clearly shows that changing HVALID proportionally changes LCD_OE high time, whereas changing HSTART, note that although
400-50 =350>180
400-300 =100<180
, the subtraction result 100 has no effect on LCD_OE high time at all, which means that HVALID doesn't change with HSTART, and there is no such equation as:
HINT ≥ HSTART + HVALID
What is even more strange is that I cannot control the position of image block displayed on LCD screen, and the actual case is that they all start from physical pixel(0,0) regardless of HSTART and VSTART value. For parallel RGB output, as the document description (see figure below) shows, the valid data area (indicated by active LCD_OE) is determined by HSTART, HVALID, VSTART and VVALID, but in actual use HVALID (and VVALID) has no effect.
Why do these happen and how can I solve the problems?
Zheng