prog8/floatproblem64-small.asm
2023-09-03 16:29:01 +02:00

81 lines
1.5 KiB
NASM

.cpu '6502'
CHROUT = $FFD2
; C64 addresses for float routines:
MOVFM = $bba2
CONUPK = $ba8c
MOVAF = $bc0c
MOVEF = $bc0f
MOVMF = $bbd4
FOUT = $bddd
FADDT = $b86a
FMULTT = $ba2b
; CX16 addresses for float routines:
;MOVFM = $fe63
;CONUPK = $fe5a
;MOVAF = $fe6c
;MOVEF = $fe81
;MOVMF = $fe66
;FOUT = $fe06
;FADDT = $fe1b
;FMULTT = $fe21
* = $0801
; 10 SYS 2062
.word (+), 10
.null $9e, " 2062"
+ .word 0
; program starts here at address 2062
lda #$8d
jsr CHROUT
ldx #0
stx $6f
lda #<prog8_float_const_1 ; 0.3
ldy #>prog8_float_const_1
jsr CONUPK ; ARG = 0.3
lda #<prog8_float_const_0 ; -0.8
ldy #>prog8_float_const_0
jsr MOVFM ; FAC1 = -0.8 ; On C64 this also seems to corrupt the value in ARG!!! (or at least, the sign of that)
jsr FADDT ; FAC1 = -0.8 + 0.3 = -0.5
; ... result in FAC1 will be wrong on C64 (1.1 instead of -0.5)....
; Seems like MOVFM (loading FAC) corrupts the sign of ARG, so CONUPK (loading ARG) needs to be done AFTER MOVFM (loading FAC)...?
; print FAC1
jsr FOUT ; fac1 to string in A/Y
sta _mod+1
sty _mod+2
ldy #0
_mod lda $ffff,y ; modified
beq +
jsr CHROUT
iny
bne _mod
+ lda #$8d
jsr CHROUT
; print expected
ldy #0
- lda string_1,y
beq +
jsr CHROUT
iny
bne -
+
loop jmp loop
string_1
.text "-.5 was expected",$8d,0
; global float constants
prog8_float_const_0 .byte $80, $cc, $cc, $cc, $cc ; float -0.8
prog8_float_const_1 .byte $7f, $19, $99, $99, $99 ; float 0.3
float_const_one .byte $81, $00, $00, $00, $00 ; float 1.0