Best Practice DLL building screen height

[Heaven/TQA]

I am little confused in terms of building screen for the 7800 with DLL. On A8 I can have any height while on 2600 i need to sync properly to the beam.

 

So question for the 7800 in Maria mode...

 

do I need to build exactly 238 scanlines in PAL even I might use less scanlines for my purpose?

 

all examples I have seen seem to pad with DLL entries to blank lines til they reach 238? I am wrong or how does Maria know when the DLL is done?

 

assume e.g. 1 screen with a text say "PLAYER 1 START" in middle of screen... do I waste empty DLLs below that text line?

 

when reading through the 7800basic manual it also has different heights as options...

[RevEng]

Have a look at the frame diagram, from The Software Guide.

 

You need to create enough DLLs to cover all non-vblank lines. (NTSC:243 or PAL:293) Otherwise the memory after your DLL will become the remainder of the DLL, and it's likely one of those entries will accidentally flag an interrupt. It's OK to have too many DLL lines, as MARIA will stop reading when VBLANK occurs.

 

The diagram shows "VISIBLE" for all non-vblank, but only the scanlines in the middle area of the diagram (between the dashed lines) is guaranteed to display on all TVs. We'll call that the "useful area". 7800basic has the option to expand the useful area past the recommendation, as most TVs can handle more.

 

For the DLLs that aren't in the useful area, you just point them all to a DL that has a terminator as it's first entry.

[Heaven/TQA]

aaah 293... now that explains that it sometimes fuck up and as you mentioned likely fire an DLI.... ok.

 

thx but stupid... same like not having a rasterline counter in hardware