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+---- Thread: ZX Assembler Inline Basic (/showthread.php?tid=171)
ZX Assembler Inline Basic - britlion - 03-04-2010
ZXB allows you to do stuff that's pretty crazy.
I had a fancy cls routine - that didn't actually clear the screen, just ran a attribute bar over the screen, and then of course you do a CLS from basic afterwards. The effect is the same, but it looks cool.
It wouldn't compile right - the call to the ZX ROM sound routine kept corrupting things. Probably messing with IX and IY registers in naughty ways.
Then it occurred to me.... just compile a beep into the middle. :-)
Look:
Code:
sub clearscreen()
asm
ld hl, 22528 ; 28000 33 0 88 10ts
ld de, 32 ; 28003 17 32 0 10ts
l_6d66: push de ; 28006 213 11ts
push hl ; 28007 229 11ts
ld de, 32 ; 28008 17 32 0 10ts
ld b, 24 ; 28011 6 22 7ts
l_6d6d: ld (hl), 24 ; Pick your leading bar attribute colour here.
add hl, de ; 28015 25 11ts
djnz l_6d6d ; 28016 16 251 8/13ts
push de ; save our registers before dropping to compiled code.
end asm
beep .05,-20
asm
pop de ; recover our register
pop hl ; (we didn't need to save HL, because we're resetting it)
push hl ; 28032 229 11ts
ld b, 24 ; 28033 6 22 7ts
l_6d83: ld (hl), 63 ; Pick you final attribute here
add hl, de ; 28037 25 11ts
djnz l_6d83 ; 28038 16 251 8/13ts
pop hl ; 28040 225 10ts
pop de ; 28041 209 10ts
dec de ; 28042 27 6ts
inc hl ; 28043 35 6ts
ld a, d ; 28044 122 4ts
or e ; 28045 179 4ts
jr nz, l_6d66 ; 28046 32 214 7/12ts
end asm
cls : rem actually wipe the bits off the screen - we just ran an attribute bar before!
end sub
CLS
Print "hello world"
pause 1
pause 0
clearscreen()
print "Hello!"How beautiful is that?
So long as I stack the registers I need (in this case DE), I can find them again when I come back. In a way, it's inline basic in the middle of assembler :-)
Anyway, that's my silliness for the day. Also: This makes for a nice clear screen subroutine. Change the bar colour and the final colour where indicated (and remember, ink and paper should be the same, so it does 'clear' it by hiding any characters on the screen until the CLS.
It's also pretty easy to change the sound (or remove it altogether - but you need something there to slow it down, or you don't see the effect. A busy loop or a pause would work too).