| 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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