prog8/floatproblem64.asm
2023-09-02 23:09:55 +02:00

145 lines
2.6 KiB
NASM

.cpu '6502'
CHROUT = $FFD2
; C64 addresses for float routines:
;MOVFM = $bba2
;CONUPK = $ba8c
;MOVAF = $bc0c
;MOVMF = $bbd4
;FOUT = $bddd
;FADDT = $b86a
;FMULTT = $ba2b
; CX16 addresses for float routines:
MOVFM = $fe63
CONUPK = $fe5a
MOVAF = $fe6c
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
; calculate: value1*one + value2*one
; (yes the multiplications with one do nothing value-wise, but they influence the routines being called...)
lda #<prog8_float_const_0 ; -0.8
ldy #>prog8_float_const_0
jsr MOVFM ; FAC1 = -0.8
lda #<float_const_one ; 1.0
ldy #>float_const_one
jsr CONUPK ; ARG = 1.0
jsr FMULTT ; FAC1 = -0.8*1.0 = -0.8
jsr pushFAC1 ; save value...
lda #<prog8_float_const_1 ; 0.3
ldy #>prog8_float_const_1
jsr MOVFM ; FAC1 = 0.3
lda #<float_const_one ; 1.0
ldy #>float_const_one
jsr CONUPK ; ARG = 1.0
jsr FMULTT ; FAC1 = 0.3*1.0 = 0.3
jsr MOVAF ; ARG = FAC1 = 0.3
jsr popFAC1 ; restore value... (-0.8)
jsr FADDT ; FAC1 = -0.8 + 0.3 = -0.5
; ... result in FAC1 will be wrong on C64 (1.1 instead of -0.5)....
; 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 -
+ rts
string_1
.text "-.5 was expected",$8d,0
floats_temp_var .byte 0,0,0,0,0 ; temporary storage for a float
pushFAC1
;-- push floating point in FAC onto the cpu stack
; save return address
pla
sta returnaddr
pla
sta returnaddr+1
ldx #<floats_temp_var
ldy #>floats_temp_var
jsr MOVMF
lda floats_temp_var
pha
lda floats_temp_var+1
pha
lda floats_temp_var+2
pha
lda floats_temp_var+3
pha
lda floats_temp_var+4
pha
; re-push return address
lda returnaddr+1
pha
lda returnaddr
pha
rts
returnaddr .word 0
popFAC1
; -- pop floating point value from cpu stack into FAC1
; save return address
pla
sta returnaddr
pla
sta returnaddr+1
pla
sta floats_temp_var+4
pla
sta floats_temp_var+3
pla
sta floats_temp_var+2
pla
sta floats_temp_var+1
pla
sta floats_temp_var
lda #<floats_temp_var
ldy #>floats_temp_var
jsr MOVFM
; re-push return address
lda returnaddr+1
pha
lda returnaddr
pha
rts
; 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