No, the frame buffer address can be switched between one of 8
locations, each 1MB large. (There is 8MB video memory) You can do
double-buffering by manipulating one of the 7 non-visible FB's and do
a switch to it. The switch to another frame buffer will be delayed
until the next vertical blank (up to 1/75th of a second) to eliminate
the possibility of your eye seeing half of the old frame and half of
the new frame for a split-second. Your application can busy-wait on
a bit to know when the next vertical refresh has occured.
Blanking the screen all black is used by our Linux framebuffer driver
on initialization, so you could steal the code from there. The
memory contents start out unitialized so this is necessary.
Actually, displaying the unitialized SDRAM as a framebuffer is a
neat -- the frame buffer will still mostly resemble the last image
shown for a minute or so before lack of SDRAM refresh cycles cause
each pixel to reach its SDRAM manufacturer chip default. All
internal capicitors on the SDRAM chip become completely discharged
due to leakage, but the encoding of no-voltage in the cap seems to
not necessarily reflect a 0 in the retreived data bit. IIRC, micron
SDRAM chips will eventually settle at 0xffff (white) on odd banks and
0x0 (black) on even banks which manifests as a series of white and
black lines on the display. Samsung chips were different.
Also, FYI, work has begun on releasing a new 800x600 video FPGA load
for the TS-7300. We can thank Peter Elliot, our forum moderator, for
help in financing this work. :-)
//Jesse Off
--- In "gamehoser" <> wrote:
>
> This topic seems to have been asleep for a while, but I've now got
my
> board and I'm looking for details on how to use the FPGA built in
> bit-blt and rectangle draw functions so that I can encorporate them
> into a graphics library I'm working on. I've got simple frame
buffer
> writes working, but a full screen bit-blt of black for example would
> be nice for a clear and given that the frame buffer address can't be
> adjusted dynamically, it'll probably be the ONLY way to have decent
> double buffering performance. Thanks in advance.
>
> James
>
> --- In "Eddie Dawydiuk" <eddie@> wrote:
> >
> > Hello,
> >
> > >> any idea where its documented that 0x21800000 is the video
base addr?
> >
> > It doesn't look like it's documented in the manual, the frame
buffer
> > driver is the only placce I see the address documented. I'll see
if we
> > can get this added to the TS-7KV manual.
> >
> > //Eddie
> >
>
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