How to center the image in PAL VGA mode?

in the Video settings when i select:
Mode: VGA
TV Standard: PAL

the image is not centered on the screen, how can i fix it?
i have noticed that in this mode ExlairXL produce a resolution of 720x576(50HZ) which is not one of the VESA standard resolution and probably that's why the screen is shifted, is there a way to fix it?

i tried to switch the TV Standard: NTSC and the video produced is 640x480 (Which is a vesa standard), but the core keep crashing so i can proceed

any tip will be appriciated

Nir

EclairXL-Ready Prompt.jpg (1.05 MB) EclairXL-Ready Prompt.jpg

Replies (12)

RE: How to center the image in PAL VGA mode? - Added by foft over 7 years ago

Hi Nir,

NTSC works on v8, but not on v7 (it shipped with v7). So if you install that you can switch modes.

Regarding resolution 'pal' mode is 576p50 and 'ntsc' mode is 480p59.94. A lot of modern monitors handle them since they are HDMI standard.

We added the dynamic pll clock chip so we can add more modes. We added the i2c chip so we can talk EDID/DDC with the monitors. These will take a while to implement. Once implemented you would probably have to craft a mode to fix your monitor.

HOWEVER there is NO standard 50Hz mode for VGA:-( Some monitors reject it entirely, some put it off centre. Really down to luck of the draw. You could try turning composite sync on/off. You could also try using 'scandoubler' mode rather the 'vga' which has somewhat different timings (scandoubled atari rather than 576p50 exactly). Or 'rgb' mode which is the 15KHz Hsync mode with original timings.

So ... errr ... basically best to look for a different monitor if you want to use PAL?

Mark

---
-- TODO -- allow ZPU to write these - simple CRTC!
process(out_pal)
begin
if (out_pal = '1') then
h_pixels_across <= 720 - 1;
h_sync_on <= 732 - 1;
h_sync_off <= 795 - 1;
h_end_count <= 864 - 1;
v_pixels_down <= 576 - 1;
v_sync_on <= 581 - 1;
v_sync_off <= 586 - 1;
v_end_count <= 625 - 1;
else
h_pixels_across <= 720 - 1;
h_sync_on <= 736 -1;
h_sync_off <= 798 -1;
h_end_count <= 858 -1;
v_pixels_down <= 480 -1;
v_sync_on <= 489 -1;
v_sync_off <= 495 -1;
v_end_count <= 525 -1;
end if;
end process;