1 | ; File name : SoftDelay.asm |
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2 | ; Project name : IDE BIOS |
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3 | ; Created date : 22.9.2007 |
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4 | ; Last update : 13.4.2010 |
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5 | ; Author : Tomi Tilli |
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6 | ; Description : Software delay loops for I/O timeout and other loops. |
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7 | |
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8 | ; Section containing code |
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9 | SECTION .text |
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10 | |
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11 | ;-------------------------------------------------------------------- |
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12 | ; There should be at least 400ns delay between outputting |
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13 | ; IDE command / drive selection and reading IDE Status Register. |
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14 | ; |
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15 | ; SoftDelay_BeforePollingStatusRegister |
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16 | ; Parameters: |
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17 | ; Nothing |
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18 | ; Returns: |
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19 | ; Nothing |
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20 | ; Corrupts registers: |
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21 | ; Nothing |
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22 | ;-------------------------------------------------------------------- |
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23 | ALIGN JUMP_ALIGN ; Cycles required |
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24 | SoftDelay_BeforePollingStatusRegister: ; 8088 | 286 | 386 | 486 |
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25 | push cx ; 15 | 3 | 2 | 1 |
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26 | mov cx, 2 ; 4 | 2 | 2 | 1 |
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27 | .DelayLoop: |
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28 | loop .DelayLoop ; | 10 | 12 | 6 |
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29 | pop cx ; 8 | 5 | 4 | 4 |
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30 | ret ; 20 | 11m| 10m| 5 |
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31 | |
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32 | |
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33 | ;-------------------------------------------------------------------- |
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34 | ; Initializes timeout counter. Timeouts are implemented using system |
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35 | ; timer ticks. First tick might take 0...54.9ms and remaining ticks |
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36 | ; will occur at 54.9ms intervals. Use delay of two (or more) ticks to |
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37 | ; ensure at least 54.9ms wait. |
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38 | ; |
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39 | ; SoftDelay_InitTimeout |
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40 | ; Parameters: |
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41 | ; CL: Number of system timer ticks before timeout |
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42 | ; DS: Segment to RAMVARS |
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43 | ; Returns: |
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44 | ; Nothing |
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45 | ; Corrupts registers: |
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46 | ; CX |
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47 | ;-------------------------------------------------------------------- |
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48 | ALIGN JUMP_ALIGN |
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49 | SoftDelay_InitTimeout: |
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50 | mov [RAMVARS.bEndTime], cl ; Store timeout ticks |
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51 | push ds |
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52 | LOAD_BDA_SEGMENT_TO ds, cx |
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53 | mov cl, [BDA.dwTimerTicks] ; Load current time lowest byte |
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54 | pop ds |
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55 | add [RAMVARS.bEndTime], cl ; Timeout to end time |
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56 | sti ; Enable interrupts |
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57 | ret |
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58 | |
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59 | |
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60 | ;-------------------------------------------------------------------- |
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61 | ; Updates timeout counter. Timeout counter can be |
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62 | ; initialized with SoftDelay_InitTimeout. |
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63 | ; |
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64 | ; SoftDelay_UpdTimeout |
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65 | ; Parameters: |
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66 | ; DS: Segment to RAMVARS |
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67 | ; Returns: |
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68 | ; CF: Set if timeout |
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69 | ; Cleared if time left |
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70 | ; Corrupts registers: |
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71 | ; Nothing |
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72 | ;-------------------------------------------------------------------- |
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73 | ALIGN JUMP_ALIGN |
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74 | SoftDelay_UpdTimeout: |
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75 | push ax |
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76 | push ds |
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77 | LOAD_BDA_SEGMENT_TO ds, ax |
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78 | mov al, [BDA.dwTimerTicks] ; Load current time lowest byte |
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79 | pop ds |
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80 | |
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81 | cmp al, [RAMVARS.bEndTime] ; End time reached? |
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82 | pop ax |
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83 | je SHORT .ReturnTimeout |
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84 | clc |
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85 | ret |
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86 | .ReturnTimeout: |
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87 | stc |
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88 | ret |
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89 | |
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90 | |
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91 | ;-------------------------------------------------------------------- |
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92 | ; Microsecond delay. |
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93 | ; Current implementation uses BIOS event wait services that are not |
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94 | ; available on XT systems. Calling overhead should be enough so it does |
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95 | ; not matter for IDE waits. On AT+ the delay will be at least 1ms since |
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96 | ; RTC resolution is 977 microsecs. |
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97 | ; |
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98 | ; SoftDelay_us |
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99 | ; Parameters: |
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100 | ; CX: Number of microsecs to wait |
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101 | ; Returns: |
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102 | ; Nothing |
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103 | ; Corrupts registers: |
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104 | ; CX |
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105 | ;-------------------------------------------------------------------- |
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106 | ALIGN JUMP_ALIGN |
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107 | SoftDelay_us: |
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108 | push dx |
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109 | push ax |
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110 | |
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111 | xor dx, dx ; Zero DX |
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112 | xchg cx, dx ; Microsecs now in CX:DX |
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113 | mov ah, 86h ; Event Wait |
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114 | int INTV_SYSTEM_SERVICES |
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115 | |
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116 | pop ax |
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117 | pop dx |
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118 | mov cx, 2 ; Prepare to wait 2 timer ticks |
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119 | jc SHORT SoftDelay_TimerTicks ; Unsupported or busy |
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120 | ret |
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121 | |
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122 | |
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123 | ;-------------------------------------------------------------------- |
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124 | ; Timer tick delay. |
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125 | ; One tick is about 54.9ms but first tick may occur anytime between |
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126 | ; 0...54.9ms! |
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127 | ; |
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128 | ; SoftDelay_TimerTicks |
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129 | ; Parameters: |
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130 | ; CX: Number of timer ticks to wait |
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131 | ; Returns: |
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132 | ; Nothing |
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133 | ; Corrupts registers: |
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134 | ; CX |
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135 | ;-------------------------------------------------------------------- |
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136 | ALIGN JUMP_ALIGN |
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137 | SoftDelay_TimerTicks: |
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138 | push ds |
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139 | push ax |
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140 | LOAD_BDA_SEGMENT_TO ds, ax |
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141 | add cx, [BDA.dwTimerTicks] ; CX to end time |
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142 | sti ; Enable interrupts |
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143 | .DelayLoop: |
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144 | cmp cx, [BDA.dwTimerTicks] ; Wait complete? |
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145 | jne SHORT .DelayLoop ; If not, loop |
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146 | pop ax |
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147 | pop ds |
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148 | ret |
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