1 | ;
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2 | ; Author:
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3 | ;
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4 | ;
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5 |
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6 | LIST P=18F452 ; directive to define processor
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7 | #include <P18F452.INC> ; processor specific variable definitions
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8 |
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9 |
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10 | CONFIG OSC = HS ; HS oscillator
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11 | CONFIG CP0 = OFF ; code protect disabled
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12 | CONFIG WDT = OFF ; Watch Dog Timer disabled
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13 | CONFIG LVP = OFF ; Single-Supply ICSP disabled
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14 |
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15 | wait_reg EQU 0x20 ; holds starting value for waiting counter
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16 |
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17 |
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18 | ORG 0x0000 ; reset vector
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19 | GOTO init
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20 |
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21 | ORG 0x0008 ; HP interrupt vector
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22 | RETFIE ; return from ISR
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23 |
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24 | ORG 0x0018 ; LP interrupt vector
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25 | RETFIE ; return from ISR
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26 |
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27 |
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28 | init CLRF PORTD, 0
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29 | CLRF TRISD, 0 ; PORTD all outputs
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30 |
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31 | CLRF PORTE, 0
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32 | SETF TRISE, 0
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33 | BCF TRISE, 0, 0
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34 | BCF TRISE, 1, 0 ; only RE0 and RE1 are outputs
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35 |
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36 | CLRF PORTB, 0
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37 | BSF TRISB,0,0 ; only RB0 is input
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38 |
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39 | CLRF ADCON1
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40 | MOVLW 0x80 ; VSS and VDD are reference voltages for ADC and...
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41 | MOVWF ADCON1,0 ; only AN0 (RA0) is analog
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42 |
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43 |
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44 | start BTFSC PORTB,0,0
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45 | GOTO init_AN1
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46 | GOTO init_AN0
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47 |
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48 |
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49 | init_AN0
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50 | CLRF ADCON0 ; select AN0 (RA0), ADC off (for now)
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51 | MOVLW 0x41
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52 | MOVWF ADCON0,0
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53 |
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54 | BSF ADCON0,2,0 ; start operation
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55 |
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56 | retry0 BTFSC ADCON0,2,0 ; poll for GO/DONE bit to be cleared
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57 | GOTO retry0 ; if not cleared, poll again
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58 |
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59 | GOTO output
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60 |
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61 | init_AN1
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62 |
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63 | CLRF ADCON0 ; select AN0 (RA0), ADC off (for now)
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64 | MOVLW 0x49
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65 | MOVWF ADCON0,0
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66 |
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67 | BSF ADCON0,2,0 ; start operation
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68 |
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69 | retry1 BTFSC ADCON0,2,0 ; poll for GO/DONE bit to be cleared
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70 | GOTO retry1 ; if not cleared, poll again
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71 |
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72 |
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73 | GOTO output
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74 |
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75 |
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76 | output MOVFF ADRESH, PORTE ; Bits 9 and 8 of result to PORTE<1:0>
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77 | MOVFF ADRESL, PORTD ; Bits 7 to 0 of result to PORTD<7:0>
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78 |
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79 | ;check GOTO check
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80 |
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81 | wait SETF wait_reg,0
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82 | NOP
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83 | NOP
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84 | NOP
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85 | NOP
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86 | NOP
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87 | NOP
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88 | NOP
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89 | NOP
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90 | DECFSZ wait_reg,0
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91 | GOTO wait
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92 | GOTO start
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93 |
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94 |
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95 | END
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