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2163
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1 NAM llio_coco3
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2 TTL CoCo 3 low-level I/O handler
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3
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4 PSECT llio_coco3,0,0,0,0,llio
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5
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6 VSECT
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7 ENDSECT
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8
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9 llio:
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10 lbsr llinit
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11 lbsr llread
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12 lbsr llwrite
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13 lbsr llterm
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14
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15 ********** I/O ROUTINES **********
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16
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17 * 6551 Parameters
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18 ADDR EQU $FF68
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19
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20 A_RXD EQU ADDR+$00
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21 A_TXD EQU ADDR+$00
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22 A_STATUS EQU ADDR+$01
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23 A_RESET EQU ADDR+$01
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24 A_CMD EQU ADDR+$02
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25 A_CTRL EQU ADDR+$03
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26
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27 * Baud rates
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28 _B2400 EQU $1A 2400 bps, 8-N-1
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29 _B4800 EQU $1C 4800 bps, 8-N-1
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30 _B9600 EQU $1E 9600 bps, 8-N-1
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31 _B19200 EQU $1F 19200 bps, 8-N-1
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32
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33 BAUD EQU _B9600
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34
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35 * ll_init - Initialize the low-level I/O
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36 * Exit: Carry = 0: Init success; Carry = 1; Init failed
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37 llinit
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38 sta A_RESET soft reset (value not important)
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39 * Set specific modes and functions:
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40 * - no parity, no echo, no Tx interrupt
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41 * - no Rx interrupt, enable Tx/Rx
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42 lda #$0B
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43 sta A_CMD save to command register
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44 lda #BAUD
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45 sta A_CTRL select proper baud rate
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46 * Read any junk rx byte that may be in the register
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47 lda A_RXD
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48 rts
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49
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50
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51 * llread - Read one character from 6551
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52 *
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53 * Entry: None
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54 * Exit: A = character that was read
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55 *
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56 * Note, this routine currently doesn't timeout
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57 llread
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58 r lda A_STATUS get status byte
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59 anda #$08 mask rx buffer status flag
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60 beq r loop if rx buffer empty
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61 lda A_RXD get byte from ACIA data port
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62 rts
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63
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64 * llwrite - Write one character to 6551
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65 *
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66 * Entry: A = character to write
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67 * Exit: None
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68 llwrite
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69 pshs a save byte to write
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70 w lda A_STATUS get status byte
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71 anda #$10 mask tx buffer status flag
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72 beq w loop if tx buffer full
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73 puls a get byte
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74 sta A_TXD save to ACIA data port
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75 rts
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76
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77
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78 llterm
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79 rts
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80
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81 IFNE 0
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82 * llwout - Write an entire string
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83 * llwerr - Write an entire string
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84 llwerr
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85 llwout
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86 pshs a
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87 l@ lda ,x+
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88 cmpa #C$CR
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89 beq e@
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90 leay -1,y
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91 beq f@
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92 bsr Write
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93 bra l@
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94 e@ bsr Write
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95 lda #C$LF
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96 bsr Write
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97 f@ ldx <buffptr
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98 clrb
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99 puls a,pc
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100
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101 * ReadLine - Read an entire string, up to CR
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102 * Entry: X = address to place string being read (CR terminated)
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103 * Y = maximum number of bytes to read (including nul byte)
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104 ReadLine
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105 ldx <buffptr
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106 pshs y,x,a
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107 ldy #80
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108 l@ bsr Read read 1 character
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109 cmpa #C$CR carriage return?
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110 beq e@ branch if so...
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111 cmpa #$08 backspace?
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112 beq bs@
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113 cmpy #$0000 anymore room?
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114 beq l@
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115 leay -1,y back up one char
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116 sta ,x+ and save in input buffer
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117 m@ bsr Write echo back out
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118 bra l@
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119 e@ sta ,x
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120 bsr Write
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121 lda #C$LF
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122 bsr Write
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123 clrb
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124 puls a,x,y,pc
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125 bs@ cmpx 1,s are we at start
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126 beq l@ if so, do nothing
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127 clr ,-x else erase last byte
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128 lbsr Write write backspace
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129 lda #C$SPAC a space...
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130 lbsr Write write it
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131 leay 1,y count back up free char
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132 lda #$08 another backspace
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133 bra m@
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134 ENDC
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135
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136 endsect
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