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2474
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1 ****************************************
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2
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3 * DECIMAL to BINARY conversion routine
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4
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5 * OTHER MODULES NEEDED: DECTAB$, IS_TERMIN
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6
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7 * ENTRY: X = start of asci decimal string terminated by
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8 * a space, comma, CR or null.
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9
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10 * EXIT: D = binary value
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11 * CC carry set if error (too large, not numeric)
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12 * Y = terminator or error char.
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13
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14 nam Convert Decimal String to Binary
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15 ttl Assembler Library Module
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16
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17
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18 psect DEC_BIN,0,0,0,0,0
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19
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20 vsect
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21 nega rmb 1
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22 endsect
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23
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24 DEC_BIN:
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25 clra set result to 0
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26 clrb
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27 pshs a,b,x
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28 leas -1,s temp variable
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29
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30 clr nega,u
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31 ldb ,x+
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32 cmpb #'-
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33 bne decbn15
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34 stb nega,u
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35 decbn1
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36 LDB ,X+ get a digit
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37 decbn15
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38 LBSR IS_DIGIT
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39 bne decbn3 end of string...
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40 INCA bump string len
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41 BRA decbn1 loop for whole string
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42
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43 decbn3
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44 lbsr IS_TERMIN valid terminator?
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45 bne error
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46
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47 ok
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48 TSTA length = 0?
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49 BEQ error yes, error
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50 CMPA #6 more than 6 chars?
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51 BHI error yes, error
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52
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53 ldx 3,s get start of string again
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54
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55 PSHS A
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56 lda ,x
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57 cmpa #'-
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58 bne decbn35
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59 leax 1,x
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60 decbn35
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61 LDA #5 max length
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62 SUBA ,S+ adjust for offset
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63 ASLA 2 bytes per table entry
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64 LEAY DECTAB$,PCR addr of conversion table
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65 LEAY A,Y add in offset for actual len
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66
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67 decbn4
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68 LDA ,X+ get a digit
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69 SUBA #$30 strip off ASCII
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70 BEQ decbn6 zero, skip
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71 sta ,s save digit=# of adds
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72 LDD 1,S get binary data
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73
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74 decbn5
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75 ADDD ,Y add in table value
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76 BCS error past 0, too big
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77 DEC ,S count down digit size
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78 BNE decbn5 loop til 0
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79 STD 1,S save binary data
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80
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81
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82 decbn6
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83 LEAY 2,Y next entry
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84 tst 1,y end of table?
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85 BNE decbn4 loop til done
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86 clr ,s+ clean up and clear carry
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87 bra exit
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88
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89
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90 error
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91 clr 0,s force data = 0
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92 clr 1,s
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93 com ,s+ clean up and set carry
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94
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95 exit
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96 tfr x,y end of string/error char
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97 puls a,b,x
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98 bcs leave
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99 tst nega,u
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100 beq leave
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101 subd #$0001
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102 coma
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103 comb
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104 andcc #$FE
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105 leave
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106 rts
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107
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108
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109 endsect
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110
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