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https://github.com/michaelcmartin/Ophis.git
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31bff0e414
More consistent set of macros for interacting, a string-reader, and better-documented preconditions based on disassemblies
246 lines
4.3 KiB
Plaintext
246 lines
4.3 KiB
Plaintext
;;; LIBBASIC64.OPH
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;;; This is a collection of routines inside the BASIC ROM that can
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;;; be repurposed to do floating-point math inside your machine
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;;; language programs. It is currently VERY EXPERIMENTAL. The documentation
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;;; available for this is spotty at best and disassembly confirms that
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;;; a lot of hidden invariants may lurk.
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;;; There's a general TODO here to generate a relatively safe and
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;;; easy to use set of macros that will do more or less what you want.
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;; BASIC functions
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.alias abs_fac1 $bc58
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.alias atn_fac1 $e30e
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.alias cos_fac1 $e264
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.alias exp_fac1 $bfed
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.alias int_fac1 $bccc
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.alias log_fac1 $b9ea
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.alias rnd_fac1 $e097
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.alias sgn_fac1 $bc39
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.alias sin_fac1 $e26b
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.alias tan_fac1 $e2b4
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;; Getting data in and out of the FACs
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.alias ld_fac1_a $bc3c
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.alias ld_fac1_s16 $b391
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.alias ld_fac1_mem $bba2
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.alias ld_fac1_fac2 $bbfc
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.alias fac1_to_string $bddd
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.alias fac1_to_s32 $bc9b
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.alias fac1_to_57 $bbca
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.alias fac1_to_5c $bbc7
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.alias ld_fac2_mem $ba8c
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.alias ld_fac2_fac1 $bc0c
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;; Unlike sgn_fac1, this returns the -1/0/1 in
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;; the accumulator
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.alias fac1_sign $bc2b
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;; FP operators. These are all FAC2 OP FAC1
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;; with the result in FAC1.
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;; PRECONDITIONS: All of these operations but AND and
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;; OR require you to have the contents of $61 in the
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;; accumulator. calling one of the ld_fac* routines
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;; will do that for you automatically. f_add_op also
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;; requires that $6F be set properly; only ld_fac2_mem
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;; does this.
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.alias f_add_op $b86a
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.alias f_subtract_op $b853
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.alias f_multiply_op $ba2b
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.alias f_divide_op $bb12
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.alias f_pow_op $bf7b
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.alias f_and_op $afe9
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.alias f_or_op $afe6
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;; Memory-based FP operations. All are MEM OP FAC1.
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;; These are usually safer than the *_op routines.
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.alias f_add_mem $b867
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.alias f_subtract_mem $b850
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.alias f_multiply_mem $ba28
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.alias f_divide_mem $bb0f
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;; Useful FP constants that live in the ROM.
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;; It's plausible that ld_fac1_a or ld_fac1_s16
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;; would be more convenient than ld_fac1_mem
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;; with f_1 or f_10, but when doing memory-based
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;; generic stuff, these will still be useful
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.alias f_0_5 $bf11 ; 0.5
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.alias f_1 $b9bc ; 1.0
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.alias f_pi $aea8 ; 3.1415926
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.alias f_10 $baf9 ; 10.0
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;; Macros to make our lives easier
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.macro f_move
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ldx #$00
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_fmvlp: lda _2,x
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sta _1,x
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inx
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cpx #$05
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bne _fmvlp
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.macend
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.macro print_str
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lda #<_1
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ldy #>_1
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jsr strout
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.macend
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.macro ld_fac1
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lda #<_1
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ldy #>_1
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jsr ld_fac1_mem
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.macend
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.macro ld_fac2
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lda #<_1
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ldy #>_1
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jsr ld_fac2_mem
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.macend
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.macro st_fac1
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lda #<_1
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ldy #>_1
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jsr fac1_to_mem
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.macend
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.macro fp_load
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`ld_fac1 _1
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.macend
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.macro fp_store
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`st_fac1 _1
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.macend
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.macro fp_print
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`ld_fac1 _1
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jsr fac1out
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.macend
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.macro fp_read
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lda #<_1
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ldy #>_1
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jsr ld_fac1_string
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.macend
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.macro fp_add
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lda #<_1
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ldy #>_1
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jsr f_add_mem
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.macend
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.macro fp_subtract
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jsr ld_fac2_fac1
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`ld_fac1 _1
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jsr f_subtract_op
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.macend
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.macro fp_multiply
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lda #<_1
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ldy #>_1
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jsr f_multiply_mem
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.macend
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.macro fp_divide
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jsr ld_fac2_fac1
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`ld_fac1 _1
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jsr f_divide_op
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.macend
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.macro fp_pow
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jsr ld_fac2_fac1
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`ld_fac1 _1
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jsr f_pow_op
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.macend
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.macro fp_and
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`ld_fac2 _1
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jsr f_and_op
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.macend
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.macro fp_or
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`ld_fac2 _1
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jsr f_or_op
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.macend
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ld_fac1_ti:
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jsr $ffde ; RDTIM
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sty $63
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stx $64
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sta $65
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;; Once the requirements on .Y and $68 are better
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;; understood, this might be exportable as
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;; ld_fac1_s32, but there are still some dragons
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;; lurking
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ldy #$00 ; Clear out intermediary values
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sta $62
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sta $68
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jmp $bcd5
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fac1_to_mem:
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sta $fd
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sty $fe
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jsr fac1_to_5c
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ldy #$00
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* lda $5c,y
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sta ($fd),y
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iny
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cpy #$05
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bne -
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rts
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ld_fac1_string:
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ldx $7a
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sta $7a
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txa
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pha
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lda $7b
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pha
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sty $7b
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jsr $79
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jsr $bcf3
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pla
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sta $7b
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pla
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sta $7a
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rts
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fac1out:
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ldy #$00 ; Clean out overflow
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sty $68
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sty $70
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jsr fac1_to_string
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ldy #$01
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;; Skip the first character if it's not "-"
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lda $100
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sec
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sbc #$2d
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beq strout
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lda #$01
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;; Fall through to strout
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;;; The BASIC ROM already has a STROUT routine - $ab1e - but
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;;; it makes use of BASIC's own temporary string handling. We
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;;; don't want it to ever touch its notion of temporary strings
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;;; here, so we provide our own short routine to do this.
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strout: sta $fd
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sty $fe
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ldy #$00
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* lda ($fd),y
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beq +
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jsr $ffd2 ; CHROUT
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iny
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bne -
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* rts
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randomize:
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jsr ld_fac1_ti
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lda #$ff
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sta $66 ; Force sign negative
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jmp rnd_fac1 ; RND(-TI)
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rnd: lda #$01
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jsr ld_fac1_a
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jmp rnd_fac1
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