... ’s linear (unlike Speccy’s screen memory), repeating the process eight times ...

... allows you to update the screen more often, at the expense ... possible "tearing" effects as the screen memory is changing mid way through ... display go directly into the memory being used by the ULA ...

... , the ULA obviously and the screen memory design. At the end of ...

... , the ULA obviously and the screen memory design. At the end of ...

... that it can update the screen memory right after that bit of ... the screen has been drawn by the ... at the bottom of the screen is actually redrawn at 50fps ...

Put it like this - when your code moves [i]anywhere[/i] other than the next line in the sequence, it searches for it from the beginning of the program.

... a requirement.

The memory is obviously tight too - less ... until you start using the screen memory. Luckily, since all RAM is ... penalty for using the screen as extra scratchpad memory where you can ...

Seems like reading from screen memory changes the floating bus value (or, maybe, not only reading, but also writing, and also from/to non-screen memory).

... ;921519"]Seems like reading from screen memory changes the floating bus value ...

... ;921519"]Seems like reading from screen memory changes the floating bus value ... , and also from/to non-screen memory).[/quote]

(...And what ...

Well, it seems simple. Reading from screen memory leads to changing the value of internal ULA register, which is read from floating bus ports. Regardless of whether the screen memory is being read by processor or ULA.

Now we need to explore how screen (and non-screen) memory reading/writing by Z80 affects to floating bus. Maybe it depends from the sort of memory - fast and slow pages, and ROM pages.

... and Y are stored in memory next to each other, so you ... ) instruction. Just remember the way memory works is if you store ...

Anyway, the usual method for Next Line up is 15 bytes;

[code]
ld a,d
dec d
and 07h
jr nz,end
ld a,e
add a,e0h
ld e,a
sbc a,a
and 08h
add a,d
ld d,a[/code]

Ah, just use Speccy (http://fms.komkon.org/Speccy) :). Press Alt+Enter to switch between full-screen and windowed modes, F12 or ESC to exist. It will remember the screen mode next time. Both DirectInput and legacy joysticks and gamepads are supported.

... commands to copy and move screen memory around. If you understand the ... screen layout of the speccy and ... "] this thread [/url] about copying memory from BASIC, you could work ...

... commands to copy and move screen memory around. If you understand the ... screen layout of the speccy and ... "] this thread [/url] about copying memory from BASIC, you could work ...

... connects the CPU, ULA, memory, and peripheral devices. It ... their code modified the screen memory accordingly. The immediate benefit ... more code during each screen update without causing flicker ... or other screen artifacts on the screen.

Do you write direct to screen memory? Would it be quicker to write to a linear part of memory and then copy to the screen? No idea, just thinking out loud.

Paddy

... easily continue printing on the next line down, though I can't ...

... did worry about that. The screen memory is two pages worth starting ...

... simple kernel subroutines for screen printing which I can ... my message on the screen at the current cursor position ... the cursor positioning (in memory addresses $1171 for Y ... can address screen memory (on the 40x25 screen) by starting at screen memory address ...

... I missing something or is line 1080 going off into Nowhereland ... has a REM comment at line 1130. It doesn't actually ... flow continues at the next line that does exist after the ...

... load the screen somewhere in memory, then move it into screen memory when ... needed. So you might load your standard screen, ... then load the map screen into a ... allow for it when reserving memory. I'm far from ...

... from a$() to screen
99 NEXT r:
NEXT p: RETURN
screen
105 RESTORE 103: ...

2000 LOAD "" SCREEN$
2003 FOR p=0 ... row from screen to a$()
2016 NEXT r:
NEXT p: RETURN ...

...
370 NEXT z

380 NEXT y
... position and size.
Line 300 runs from top ... edge.
Line 320 draws a solid line from left- ... loops around to do the next line. But before we do ... :

Line 330 protects us from dividing ...

That's what I would do too, a quick LDIR to copy it to screen memory. :)

... have left between the two screen banks.

One ... ZX-HD replicate the Spectrum screen memory for producing their video ... ) display the 128K shadow screen whilst the normal Spectrum ULA ... frames together, so with 128K screen-flipping, again you could ...

... bank switch either or both screen memory areas out of the CPU ... . As well as switching either screen area into either the normal ... screen RAM CPU address area, or in the high memory area ... have had the same banked memory arrangement as the earlier 128k ...