/usr/share/z88dk/lib/zx81_altint.def is in z88dk-data 1.8.ds1-10.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 | ; CRT0 for the ZX81 - SLOW MODE
;
;
; ----------------------------------------------------------------------------------------
; Modified display handler to preserve IY
; Note: a swap between IX and IY happens "on the fly" during assembly !
; ----------------------------------------------------------------------------------------
;
; Stefano Bodrato Sept. 2007
; Sync fixed by Siegfried Engel - Dec. 2007
;
; - - - - - - -
;
; $Id: zx81_altint.def,v 1.7 2007/12/18 13:35:51 stefano Exp $
;
; - - - - - - -
;--------------------------------------------------------------
;--------------------------------------------------------------
XDEF hrg_on
XDEF hrg_off
;========
; Not HRG really, but switches the new interrupt handler with no sighs
;========
hrg_on:
call $F2B ; SLOW
ld hl,L0281
push hl
jr HRG_Sync
hrg_off:
ld hl,$281
push hl
;ld a,$1e
;ld i,a
HRG_Sync:
ld hl,$4034 ; FRAMES counter
ld a,(hl) ; get old FRAMES
HRG_Sync1:
cp (hl) ; compare to new FRAMES
jr z,HRG_Sync1 ; exit after a change is detected
pop iy ; switch to new display handler
ret
;--------------------------------------------------------------
;--------------------------------------------------------------
;; DISPLAY-1
L0229:
LD HL,($4034) ; fetch two-byte system variable FRAMES.
DEC HL ; decrement frames counter.
;; DISPLAY-P
L022D: LD A,$7F ;
AND H ;
OR L ;
LD A,H ;
JR NZ,L0237 ; to ANOTHER
RLA ;
JR L0239 ; to OVER-NC
; ---
;; ANOTHER
L0237: LD B,(HL) ;
SCF ; Set Carry Flag
;; OVER-NC
L0239: LD H,A ;
LD ($4034),HL ; sv FRAMES_lo
RET NC ;
;; DISPLAY-2
L023E:
push ix
ld ix,16384
CALL $2BB ; routine KEYBOARD
pop ix
LD BC,($4025) ; sv LAST_K
LD ($4025),HL ; sv LAST_K
LD A,B ;
ADD A,$02 ;
SBC HL,BC ;
LD A,($4027) ; sv DEBOUNCE
OR H ;
OR L ;
LD E,B ;
LD B,$0B ;
LD HL,$403B ; system variable CDFLAG
RES 0,(HL) ;
JR NZ,L0264 ; to NO-KEY
BIT 7,(HL) ;
SET 0,(HL) ;
RET Z ;
DEC B ;
NOP ;
SCF ; Set Carry Flag
;; NO-KEY
L0264: LD HL,$4027 ; sv DEBOUNCE
CCF ; Complement Carry Flag
RL B ;
;; LOOP-B
L026A: DJNZ L026A ; to LOOP-B
LD B,(HL) ;
LD A,E ;
CP $FE ;
SBC A,A ;
LD B,$1F ;
OR (HL) ;
AND B ;
RRA ;
LD (HL),A ;
OUT ($FF),A ;
LD HL,($400C) ; sv D_FILE_lo
SET 7,H ;
CALL L0292 ; routine DISPLAY-3
; ---
;; R-IX-1
L0281: LD A,R ;
LD BC,$1901 ;
LD A,$F5 ;
CALL $2B5 ; routine DISPLAY-5
DEC HL ;
CALL L0292 ; routine DISPLAY-3
; ---
;; R-IX-2
L028F: JP L0229 ; to DISPLAY-1
; ---
;; DISPLAY-3
L0292: POP IY ; return address to IX register (-IXIY swap).
; will be either L0281 or L028F - see above.
; Modified here to keep IY unchanged
ld a,(16424) ; load C with MARGIN
ld c,a
ld a,(16443) ; test CDFLAG
bit 7,a
jp z,$2a9
ld a,c
neg
inc a
ex af,af
out ($FE),a
ld hl,(frames) ; clock handler
inc hl
ld (frames),hl
ld a,h
or l
jp nz,nofr1
ld hl,frames+1
inc (hl)
.nofr1
jp $2A4
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