A83: Re: Bit Masking

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A83: Re: Bit Masking

"and" automatically sets the Z flag if the number is equal , using that number of significant bits.
ie...
 ld a,%111
 and %111
 jp z,label        ; the z-flag would be set
 
 ld a,%101
 and %111
 jp z,label        ; the z-flag would not be set, because the 3 significant bits are not all the same
 
 ld a,%10111
 and %111
 jp z,label        ; it would jump to the label... because the last 3 bits in a = "%111"

-Harper Maddox
 
jerky@ebicom.net
-----Original Message-----
From: James Matthews <matthews@tkb.att.ne.jp>
To: assembly-83@lists.ticalc.org <assembly-83@lists.ticalc.org>
Date: Friday, March 20, 1998 10:10 PM
Subject: A83: Bit Masking


Harper:

Great routine...I didn't understand two lines of code (well one really...)

> and %1  ;is it at 0 (when we only want 1 or 0)
> jr nz,norm ; goto "norm" if temp isnt equal to 2

Now, in that first line -- that's a bit mask, right?  And % stands for
binary?  So, you take the binary number where?, and 'AND' it with 00000001.
So, what is the JR routine using to check?

James.

____________________

James Matthews.
E-mail (family):    matthews@tkb.att.ne.jp
E-mail (private):  james_matthews@hotmail.com

Homepage:  http://home.att.ne.jp/gold/tomcat21/index2.html
ICQ:  7413754
____________________________________

----------
From: Harper Maddox <jerky@ebicom.net>
To: assembly-83@lists.ticalc.org
Subject: A83: Re: flashtext
Date: Saturday, March 21, 1998 10:17 AM

I used this in avalanch and Chicken Shoot...
;-------A cool routine devised by Harper Maddox and Andrew
Ungvarsky------------
; Displays a flashing "Press 2nd"

ld c,0
introwait:
ld b,21
loop:
halt
call getkey
cp 45   ; clear???
ret z   ; return to what called the program... The OS
cp 21
jr z,start  ; If key="2nd" then start the game
djnz loop

push bc
;-------erase reverse line to left of "Press 2nd"
ld bc,16*256+15   ; start of line = (15,16)
ld de,16*256+8    ; end of line = (8,16)
ld h,0            ; 0 means draw a white line
call _iline       ; draw the line
;-----end erase line----------
pop bc
inc c
ld a,c
and %1  ;is it at 0 (when we only want 1 or 0)
jr nz,norm ; goto "norm" if temp isnt equal to 2
set textinverse,(iy+textflags)   ; Flash... inverse text is on
norm:
ld a,3   ; Home screen text starts at (6,3)
ld (curcol),a
ld a,6
ld (currow),a
ld hl,secnd    
call _puts ; display the "secnd" string
res textinverse,(iy+textflags) ; turn Text Inverse off

jr introwait    ; return back to the intro loop

getkey:
call _zerooop1
call _getk
call _op2toop1
call _convop1
ld a,e
jr z,getkey
ret

-Harper Maddox

jerky@ebicom.net
    -----Original Message-----
    From: Dustin Graham <ima_macuser@hotmail.com>
    To: assembly-83@lists.ticalc.org <assembly-83@lists.ticalc.org>
    Date: Friday, March 20, 1998 4:09 PM
    Subject: A83: flashtext
   
   
   
    ;try this-I think it will work
   
    prog_start:
        set textInverse,(iy+textflags)
        CALL _CLRLCDFULL      ;CLEAR SCREEN
        LD HL,0202h
        ld (currow),hl
        LD HL,Madeby
        CALL _PUTS
        jr    LOOP
        res textInverse,(iy+textflags)
        CALL _CLRLCDFULL      ;CLEAR SCREEN
        LD HL,0202h
        ld (currow),hl
        LD HL,Madeby
        CALL _PUTS
        CALL gk
   
    gk:
        call _GetKy
        or a
        jr z,prog_start
        ret nz
   
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