source: xtideuniversalbios/trunk/Configurator/Src/Flash.asm

; Project name  :   XTIDE Univeral BIOS Configurator
; Description   :   Function for flashing the EEPROM.

; Section containing code
SECTION .text

;--------------------------------------------------------------------
; Loads old XTIDE Universal BIOS settings from ROM to RAM.
;
; EEPROM_LoadSettingsFromRomToRam
;   Parameters:
;       Nothing
;   Returns:
;       Nothing
;   Corrupts registers:
;       BX, CX, ES
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
Flash_CopyCurrentContentsForComparison:
    push    ds
    push    di
    push    si

    call    EEPROM_GetComparisonBufferPointerToDSBX
    push    ds
    pop     es
    mov     di, bx                                      ; Comparison buffer now in ES:DI
    xor     si, si
    mov     ds, [cs:g_cfgVars+CFGVARS.wEepromSegment]   ; EEPROM now in DS:SI
    mov     cx, [cs:g_cfgVars+CFGVARS.wEepromSize]
    shr     cx, 1           ; Byte count to word count
    cld                                                 ; MOVSW to increment DI and SI
    rep movsw

    pop     si
    pop     di
    pop     ds
    ret


;--------------------------------------------------------------------
; Verifies that all data has been written successfully.
;
; Flash_WasDataWriteSuccessful
;   Parameters:
;       Nothing
;   Returns:
;       ZF:     Set if data was written successfully
;               Cleared if write failed
;   Corrupts registers:
;       CX, ES
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
Flash_WasDataWriteSuccessful:
    push    ds
    push    di
    push    si

    call    EEPROM_GetSourceBufferPointerToDSSI
    call    EEPROM_GetEepromPointerToESDI
    mov     cx, [cs:g_cfgVars+CFGVARS.wEepromSize]
    shr     cx, 1           ; Byte count to word count
    cld                     ; CMPSW to increment SI and DI
    repe cmpsw

    pop     si
    pop     di
    pop     ds
    ret


;--------------------------------------------------------------------
; Writes page of data to EEPROM.
;
; Flash_WritePage
;   Parameters:
;       AX:     SDP command
;       CX:     Page size (1, 2, 4, 8, 16, 32 or 64 bytes)
;       DS:BX:  Ptr to comparison buffer with old EEPROM data
;       DS:SI:  Ptr to source data to write
;       ES:DI:  Ptr to destination EEPROM
;   Returns:
;       BX, SI, DI: Updated to next page
;       CF:     Cleared if page written successfully
;               Set if polling timeout
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
Flash_WritePage:
    call    Flash_DoesPageNeedToBeWritten
    jz      SHORT .ReturnWithoutWriting
    push    bp
    push    cx
    push    ax

    mov     bp, .LoopWritePageBytes ; Return address from SDP command
    cli                             ; Disable interrupts
    jmp     SHORT Flash_WriteSdpCommand

ALIGN JUMP_ALIGN
.LoopWritePageBytes:
    lodsb                           ; Load source byte to AL, increment SI
    cmp     al, [bx]                ; Trying to write existing data?
    je      SHORT .SkipByte
    inc     bx                      ; Increment comparison buffer pointer
    mov     ah, al                  ; Last byte written to AH
    mov     bp, di                  ; ES:BP points to last byte written
    stosb                           ; Write source byte to EEPROM, increment DI
    loop    .LoopWritePageBytes
    jmp     SHORT .PageCompleted
ALIGN JUMP_ALIGN
.SkipByte:
    inc     bx
    inc     di
    loop    .LoopWritePageBytes

ALIGN JUMP_ALIGN
.PageCompleted:
    sti                             ; Enable interrupts
    call    Flash_PollEepromUntilWriteCycleHasCompleted
    pop     ax
    pop     cx
    pop     bp
    ret

ALIGN JUMP_ALIGN
.ReturnWithoutWriting:
    add     bx, cx
    add     si, cx
    add     di, cx
    clc
    ret

;--------------------------------------------------------------------
; Compares source data and comparison buffer.
;
; Flash_DoesPageNeedToBeWritten
;   Parameters:
;       CX:     Page size (1, 2, 4, 8, 16, 32 or 64 bytes)
;       DS:BX:  Ptr to comparison buffer with old EEPROM data
;       DS:SI:  Ptr to source data to write
;   Returns:
;       ZF:     Set if no need to write page
;               Cleared if writing is needed
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
Flash_DoesPageNeedToBeWritten:
    push    es
    push    di
    push    si
    push    cx

    push    ds
    pop     es
    mov     di, bx              ; ES:DI now points to comparison buffer
    cld                         ; CMPSB to increment SI and DI
    repe cmpsb

    pop     cx
    pop     si
    pop     di
    pop     es
    ret


;--------------------------------------------------------------------
; Writes Software Data Protection command to EEPROM.
;
; Flash_WriteSdpCommand
;   Parameters:
;       AX:     SDP command
;       BP:     Return address
;       ES:     Segment to EEPROM
;   Returns:
;       Nothing
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
Flash_WriteSdpCommand:
    cmp     ax, CMD_SDP_ENABLE
    je      SHORT Flash_WriteSdpEnableCommand
    cmp     ax, CMD_SDP_DISABLE
    je      SHORT Flash_WriteSdpDisableCommand
    jmp     bp

ALIGN JUMP_ALIGN
Flash_WriteSdpEnableCommand:
    mov     BYTE [es:1555h], 0AAh   ; Write AAh to address 1555h
    mov     BYTE [es:0AAAh], 55h    ; Write 55h to address 0AAAh
    mov     BYTE [es:1555h], 0A0h   ; Write A0h to address 1555h
    jmp     bp

ALIGN JUMP_ALIGN
Flash_WriteSdpDisableCommand:
    mov     BYTE [es:1555h], 0AAh   ; Write AAh to address 1555h
    mov     BYTE [es:0AAAh], 55h    ; Write 55h to address 0AAAh
    mov     BYTE [es:1555h], 80h    ; Write 80h to address 1555h
    mov     BYTE [es:1555h], 0AAh   ; Write AAh to address 1555h
    mov     BYTE [es:0AAAh], 55h    ; Write 55h to address 0AAAh
    mov     BYTE [es:1555h], 20h    ; Write 20h to address 1555h
    jmp     bp


;--------------------------------------------------------------------
; Polls EEPROM until write cycle ends.
;
; Flash_PollEepromUntilWriteCycleHasCompleted
;   Parameters:
;       AH:     Last byte written
;       ES:BP:  Ptr to EEPROM last write location
;   Returns:
;       CF:     Cleared if polling successful
;               Set if polling timeout
;   Corrupts registers:
;       AX, CX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
Flash_PollEepromUntilWriteCycleHasCompleted:
    call    Flash_InitializePollingTimeout
ALIGN JUMP_ALIGN
.PollLoop:
    mov     al, [es:bp]             ; Load byte from EEPROM
    and     ax, 8080h               ; Clear all but bit 7 from both bytes
    cmp     al, ah                  ; Same bytes?
    je      SHORT .Return
    call    Flash_UpdatePollingTimeout
    jnc     SHORT .PollLoop         ; Not timeout
ALIGN JUMP_ALIGN
.Return:
    ret

;--------------------------------------------------------------------
; Initializes timeout counter. Timeouts are implemented using system
; timer ticks. First tick might take 0...54.9ms and remaining ticks
; will occur at 54.9ms intervals. Use delay of two (or more) ticks to
; ensure at least 54.9ms wait.
;
; Flash_InitializePollingTimeout
;   Parameters:
;       Nothing
;   Returns:
;       CX:     Timeout end time for Flash_UpdatePollingTimeout
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
Flash_InitializePollingTimeout:
    push    ds
    LOAD_BDA_SEGMENT_TO ds, cx
    mov     cx, CNT_TMEOUT_POLL
    add     cx, [BDA.dwTimerTicks]      ; CX = End time
    pop     ds
    sti                                 ; Enable interrupts
    ret

;--------------------------------------------------------------------
; Updates timeout counter. Timeout counter can be
; initialized with Flash_InitializePollingTimeout.
;
; Flash_UpdatePollingTimeout
;   Parameters:
;       CX:     Timeout end time
;   Returns:
;       CF:     Set if timeout
;               Cleared if time left
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
Flash_UpdatePollingTimeout:
    push    ds
    push    ax
    LOAD_BDA_SEGMENT_TO ds, ax
    cmp     cx, [BDA.dwTimerTicks]      ; Timeout?
    pop     ax
    pop     ds
    je      SHORT .ReturnTimeout
    clc
    ret
.ReturnTimeout:
    stc
    ret