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2474
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1 *****************************************
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2
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3 * Hexadecimal string to BINARY conversion
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4
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5 * OTHER MODULES REQUIRED: TO_UPPER, IS_TERMIN, IS_XDIGIT
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6
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7 * ENTRY: X=start of a hex string terminated by a space,
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8 * comma, CR, or NULL.
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9
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10 * EXIT: D=binary number
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11 * CC carry set iferror (too large, non-numeric)
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12 * Y=terminator position or error char.
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13
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14
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15 nam Convert Hex String to Binary
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16 ttl Assembler Library Module
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17
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18 psect HEX_BIN,0,0,0,0,0
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19
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20
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21 HEX_BIN:
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22 clra init number
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23 clrb
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24 pshs d,x
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25 tfr d,y digit counter
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26
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27 loop
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28 ldb ,x+ get next digit
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29 lbsr TO_UPPER convert to uppercase
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30 lbsr IS_TERMIN end of string?
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31 beq exit yes, go home
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32 lbsr IS_XDIGIT make sure it's valid digit
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33 bne error not 0..9, a..f
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34 cmpb #'9 convert to binary value
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35 bls notAtoF
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36 subb #7 fix a..f
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37 notAtoF
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38 subb #'0 convert to binary 0..15
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39
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40 * now shift the digit to bits 7..4
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41
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42 lslb
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43 lslb
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44 lslb
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45 lslb
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46
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47 * now shift the value in to the result
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48
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49 lda #4 number of bits
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50 l1
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51 lslb digit bit to carry
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52 rol 1,s carry bit to result
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53 rol 0,s
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54 deca done 4?
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55 bne l1 no, loop
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56
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57 leay 1,y number of digits done
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58 cmpy #4
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59 bhi error more than 4
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60 bra loop keep going
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61
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62
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63 exit
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64 clrb clear carry=no error
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65 sty -2,s test y (count)
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66 bne done no digits?
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67
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68 error
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69 clr 0,s
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70 clr 1,s
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71 orcc #1 set carry
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72
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73 done
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74 leay -1,x terminator/error pos
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75 puls d,x,pc
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76
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77 endsect
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78
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79 |
