mirror of
https://github.com/michaelcmartin/Ophis.git
synced 2024-12-04 23:52:16 +00:00
Add libbasic64, for using BASIC's floating point in assembler programs
This commit is contained in:
parent
60f03a34af
commit
72d86ea06d
170
platform/libbasic64.oph
Normal file
170
platform/libbasic64.oph
Normal file
@ -0,0 +1,170 @@
|
||||
;;; LIBBASIC64.OPH
|
||||
|
||||
;;; This is a collection of routines inside the BASIC ROM that can
|
||||
;;; be repurposed to do floating-point math inside your machine
|
||||
;;; language programs. It is currently VERY EXPERIMENTAL. The documentation
|
||||
;;; available for this is spotty at best and disassembly confirms that
|
||||
;;; a lot of hidden invariants may lurk.
|
||||
|
||||
;;; There's a general TODO here to generate a relatively safe and
|
||||
;;; easy to use set of macros that will do more or less what you want.
|
||||
|
||||
;; BASIC functions
|
||||
.alias abs_fac1 $bc58
|
||||
.alias atn_fac1 $e30e
|
||||
.alias cos_fac1 $e264
|
||||
.alias exp_fac1 $bfed
|
||||
.alias int_fac1 $bccc
|
||||
.alias log_fac1 $b9ea
|
||||
.alias rnd_fac1 $e097
|
||||
.alias sgn_fac1 $bc39
|
||||
.alias sin_fac1 $e26b
|
||||
.alias tan_fac1 $e2b4
|
||||
|
||||
;; Getting data in and out of the FACs
|
||||
.alias ld_fac1_a $bc3c
|
||||
.alias ld_fac1_s16 $b391
|
||||
.alias ld_fac1_mem $bba2
|
||||
.alias ld_fac1_fac2 $bbfc
|
||||
.alias fac1_to_string $bddd
|
||||
.alias fac1_to_s32 $bc9b
|
||||
.alias fac1_to_57 $bbca
|
||||
.alias fac1_to_5c $bbc7
|
||||
|
||||
.alias ld_fac2_mem $ba8c
|
||||
.alias ld_fac2_fac1 $bc0c
|
||||
|
||||
;; Unlike sgn_fac1, this returns the -1/0/1 in
|
||||
;; the accumulator
|
||||
.alias fac1_sign $bc2b
|
||||
|
||||
;; FP operators. These are all FAC2 OP FAC1
|
||||
;; with the result in FAC1.
|
||||
.alias f_plus $b86a
|
||||
.alias f_minus $b853
|
||||
.alias f_times $ba2b
|
||||
.alias f_div $bb12
|
||||
.alias f_pow $bf7b
|
||||
.alias f_and $afe9
|
||||
.alias f_or $afe6
|
||||
|
||||
;; Memory-based FP operations. All are MEM OP FAC1.
|
||||
;; These seem safer; FAC2 seems to have some slippery
|
||||
;; invariants in it.
|
||||
.alias f_add $b867
|
||||
.alias f_subtract $b850
|
||||
.alias f_multiply $ba28
|
||||
.alias f_divide $bb0f
|
||||
|
||||
;; Useful FP constants that live in the ROM.
|
||||
;; It's plausible that ld_fac1_a or ld_fac1_s16
|
||||
;; would be more convenient than ld_fac1_mem
|
||||
;; with f_1 or f_10, but when doing memory-based
|
||||
;; generic stuff, these will still be useful
|
||||
.alias f_0_5 $bf11 ; 0.5
|
||||
.alias f_1 $b9bc ; 1.0
|
||||
.alias f_pi $aea8 ; 3.1415926
|
||||
.alias f_10 $baf9 ; 10.0
|
||||
|
||||
;; Macros to make our lives easier
|
||||
.macro f_move
|
||||
ldx #$00
|
||||
_fmvlp: lda _2,x
|
||||
sta _1,x
|
||||
inx
|
||||
cpx #$05
|
||||
bne _fmvlp
|
||||
.macend
|
||||
|
||||
.macro print_str
|
||||
lda #<_1
|
||||
ldy #>_1
|
||||
jsr strout
|
||||
.macend
|
||||
|
||||
.macro ld_fac1
|
||||
lda #<_1
|
||||
ldy #>_1
|
||||
jsr ld_fac1_mem
|
||||
.macend
|
||||
|
||||
.macro ld_fac2
|
||||
lda #<_1
|
||||
ldy #>_1
|
||||
jsr ld_fac2_mem
|
||||
.macend
|
||||
|
||||
.macro st_fac1
|
||||
lda #<_1
|
||||
ldy #>_1
|
||||
jsr fac1_to_mem
|
||||
.macend
|
||||
|
||||
.macro print_f
|
||||
`ld_fac1 _1
|
||||
jsr fac1out
|
||||
.macend
|
||||
|
||||
ld_fac1_ti:
|
||||
jsr $ffde ; RDTIM
|
||||
sty $63
|
||||
stx $64
|
||||
sta $65
|
||||
;; Once the requirements on .Y and $68 are better
|
||||
;; understood, this might be exportable as
|
||||
;; ld_fac1_s32, but there are still some dragons
|
||||
;; lurking
|
||||
ldy #$00 ; Clear out intermediary values
|
||||
sta $62
|
||||
sta $68
|
||||
jmp $bcd5
|
||||
|
||||
fac1_to_mem:
|
||||
sta $fd
|
||||
sty $fe
|
||||
jsr fac1_to_5c
|
||||
ldy #$00
|
||||
* lda $5c,y
|
||||
sta ($fd),y
|
||||
iny
|
||||
cpy #$05
|
||||
bne -
|
||||
rts
|
||||
|
||||
fac1out:
|
||||
ldy #$00 ; Clean out overflow
|
||||
sty $68
|
||||
sty $70
|
||||
jsr fac1_to_string
|
||||
ldy #$01
|
||||
;; Skip the first character if it's not "-"
|
||||
lda $100
|
||||
sec
|
||||
sbc #$2d
|
||||
beq strout
|
||||
lda #$01
|
||||
;; Fall through to strout
|
||||
|
||||
;;; The BASIC ROM already has a STROUT routine - $ab1e - but
|
||||
;;; it makes use of BASIC's own temporary string handling. We
|
||||
;;; don't want it to ever touch its notion of temporary strings
|
||||
;;; here, so we provide our own short routine to do this.
|
||||
strout: sta $fd
|
||||
sty $fe
|
||||
ldy #$00
|
||||
* lda ($fd),y
|
||||
beq +
|
||||
jsr $ffd2 ; CHROUT
|
||||
iny
|
||||
bne -
|
||||
* rts
|
||||
|
||||
randomize:
|
||||
jsr ld_fac1_ti
|
||||
lda #$ff
|
||||
sta $66 ; Force sign negative
|
||||
jmp rnd_fac1 ; RND(-TI)
|
||||
|
||||
rnd: lda #$01
|
||||
jsr ld_fac1_a
|
||||
jmp rnd_fac1
|
Loading…
Reference in New Issue
Block a user