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Forums > C64 Coding > keep top 2 rows of screen from vertical scrolling
2021-07-19 03:09
TheWarCriminal

Registered: May 2011
Posts: 16
keep top 2 rows of screen from vertical scrolling

I lost my code from years ago that would keep the top 2 rows of the character screen (1024+80) from vertical scrolling with no flickering. I used it for the BBS I was creating back then. With recent devs in CBASE not performing how I would like it too I have started back recoding that BBS but I need 2 very important things. First off is a no vertical scroll on the top 2 rows. I know CBASE has one but it flickers and is compiled. Would like one in ML or someone point me in a starting direction. The 2nd one is a date ML routine. I know how to check the time and convert it into a readable format but the timer does not hold a date so it keeps resetting at 24hr. Since I am coding this BBS for WinVice is there a way to get the info from the emulated RTC?

I know this sounds like I have no clue what I am doing but when you have been away from c64 coding for 3 decades you loose the knowledge. Just getting reacquainted with BASIC V2 is a hazzle when you are so used to VB.NET behind code. One oh the things that constantly get me is the string setup: BASIC V2 is string$ where as VB.NET is $string. Which ever company decided to screw around with the context should have left it alone.

Any help would be appreciated in this. (I have searched the forums here, Google and Internet Archive c64 Books)
 
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2021-07-21 12:40
Groepaz

Registered: Dec 2001
Posts: 9973
Oh yeah, border sprites with RS232 NMI going on \o/
2021-07-21 12:47
ChristopherJam

Registered: Aug 2004
Posts: 1174
Quoting Krill
Quoting Groepaz
Don't forget to patch the HOME location too
Or just have prints all ordinary on 40x25, but with a split that would optionally display a hires bitmap in the top two rows (no $d800 issue).


Yes, I think Silver Dream already mentioned raster splits.

(much as you already mentioned stealing the kernal routine - though I was thinking more, disable ROM and patch the kernal routine, so scroll is still triggered by character printing as usual)

Nice idea using hires bitmap to avoid d800 issues though!

I'm still unclear as to whether he wants to do smooth scrolling or just the usual row resolution scrolling.
2021-07-21 12:51
Krill

Registered: Apr 2002
Posts: 1974
Quoting ChristopherJam
though I was thinking more, disable ROM and patch the kernal routine, so scroll is still triggered by character printing as usual
Somebody mentioned memory being tight, so i guess hooking into the CHROUT vector and doing some interception and custom scroll etc. seems more feasible than hogging 8 KB for pretty much the same functionality. =)
2021-07-21 12:54
Krill

Registered: Apr 2002
Posts: 1974
Quoting Groepaz
Oh yeah, border sprites with RS232 NMI going on \o/
Same problem as with a raster split, no? But can be turned off for transfers.

And i guess you wouldn't really use actual NMI but poll the flag from mainline thread instead (for maximum transfer speed)?
2021-07-21 13:46
Silver Dream !

Registered: Nov 2005
Posts: 73
Quoting ChristopherJam
(much as you already mentioned stealing the kernal routine - though I was thinking more, disable ROM and patch the kernal routine, so scroll is still triggered by character printing as usual)
That was actually the very first suggestion I came with. The question is whether RAM under KERNAL is to be used for something else than a KERNAL copy. Hooking through IBSOUT as suggested by Krill is more complex but surely uses less than 8KiB needed for KERNAL patching.

Quote:
Nice idea using hires bitmap to avoid d800 issues though!
Yes, although also rather pricey both in terms of memory and cpu usage.

Quote:
I'm still unclear as to whether he wants to do smooth scrolling or just the usual row resolution scrolling.
Good that it's not only me who has doubts on the actual OP's goal :-)
2021-07-21 14:17
Groepaz

Registered: Dec 2001
Posts: 9973
Quote:

Same problem as with a raster split, no? But can be turned off for transfers.

And i guess you wouldn't really use actual NMI but poll the flag from mainline thread instead (for maximum transfer speed)?

He wants to have this statusline to watch when a user is connected to the BBS. That pretty much implies you are using NMIs and cant switch them off - unless you limit yourself to support a certain kind of rs232 interface (no userport bitbanging, for example). And no, the most efficient implementation has the NMI fill a ringbuffer, and the main thread consuming that.
2021-07-21 16:00
Silver Dream !

Registered: Nov 2005
Posts: 73
Quoting Groepaz
Oh yeah, border sprites with RS232 NMI going on \o/
Is that a problem or what? :-P
2021-07-23 12:01
Krill

Registered: Apr 2002
Posts: 1974
Quoting Silver Dream !
Quoting Groepaz
Oh yeah, border sprites with RS232 NMI going on \o/
Is that a problem or what? :-P
Maybe just a different kind of flicker, maybe no problem at all (opening the vertical borders has a large margin of tolerance).

Additional DMA itself (caused by the sprites) on top of badline DMA shouldn't be a problem at all, should it? :)
2021-07-23 12:38
Groepaz

Registered: Dec 2001
Posts: 9973
Oh when Krill mentions borders i was thinking of sideborder, of course. Vertical is no problem, obviously :=)
2021-07-23 18:33
Count Zero

Registered: Jan 2003
Posts: 1398
OP should clarify what he actually wants to achieve or if one of the excessive answers already resolves his problem.

THEN we go into creation a sideborder display for a session trace, the IP and a traceroute of the currently logged on user.
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