source: xtideuniversalbios/trunk/XTIDE_Universal_BIOS/Src/Device/Serial/SerialCommand.asm @ 181

; Project name  :   XTIDE Universal BIOS
; Description   :   Serial Device Command functions.

; Section containing code
SECTION .text

;--------------- UART Equates -----------------------------
;
; Serial Programming References:
;    http://en.wikibooks.org/wiki/Serial_Programming
;

SerialCommand_UART_base                         EQU     0
SerialCommand_UART_transmitByte                 EQU     0
SerialCommand_UART_receiveByte                  EQU     0
SerialCommand_UART_divisorLow                   EQU     0
; Values for UART_divisorLow:
; 60h = 1200, 30h = 2400, 18h = 4800, 0ch = 9600, 6 = 19200, 3 = 38400, 2 = 57600, 1 = 115200

SerialCommand_UART_divisorLow_startingBaud      EQU   030h
; We support 4 baud rates, starting here going higher and skipping every other baud rate
; Starting with 30h, that means 30h (1200 baud), 0ch (9600 baud), 3 (38400 baud), and 1 (115200 baud)
; Note: hardware baud multipliers (2x, 4x) will impact the final baud rate and are not known at this level

SerialCommand_UART_interruptEnable              EQU     1
SerialCommand_UART_divisorHigh                  EQU     1
; UART_divisorHigh is zero for all speeds including and above 1200 baud

SerialCommand_UART_interruptIdent               EQU     2
SerialCommand_UART_FIFOControl                  EQU     2

SerialCommand_UART_lineControl                  EQU     3

SerialCommand_UART_modemControl                 EQU     4

SerialCommand_UART_lineStatus                   EQU     5

SerialCommand_UART_modemStatus                  EQU     6

SerialCommand_UART_scratch                      EQU     7

SerialCommand_PackedPortAndBaud_StartingPort    EQU     240h
SerialCommand_PackedPortAndBaud_PortMask        EQU     0fch    ; upper 6 bits - 240h through 438h
SerialCommand_PackedPortAndBaud_BaudMask        EQU     3       ; lower 2 bits - 4 baud rates

SerialCommand_Protocol_Write                    EQU     3
SerialCommand_Protocol_Read                     EQU     2
SerialCommand_Protocol_Inquire                  EQU     0
SerialCommand_Protocol_Header                   EQU     0a0h

;--------------------------------------------------------------------
; SerialCommand_OutputWithParameters
;   Parameters:
;       BH:     Non-zero if 48-bit addressing used
;               (ignored at present as 48-bit addressing is not supported)
;       BL:     IDE Status Register bit to poll after command
;               (ignored at present, since there is no IDE status register to poll)
;       ES:SI:  Ptr to buffer (for data transfer commands)
;       DS:DI:  Ptr to DPT (in RAMVARS segment)
;       SS:BP:  Ptr to IDEREGS_AND_INTPACK
;   Returns:
;       AH:     INT 13h Error Code
;       CF:     Cleared if success, Set if error
;   Corrupts registers:
;       AL, BX, CX, DX, (ES:SI for data transfer commands)
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
SerialCommand_OutputWithParameters:

        mov     ah,(SerialCommand_Protocol_Header | SerialCommand_Protocol_Read)

        mov     al,[bp+IDEPACK.bCommand]

        cmp     al,20h          ; Read Sectors IDE command
        jz      .readOrWrite
        inc     ah              ; now SerialCommand_Protocol_Write
        cmp     al,30h          ; Write Sectors IDE command
        jz      .readOrWrite

;  all other commands return success
;  including function 0ech which should return drive information, this is handled with the identify functions
        xor     ah,ah           ;  also clears carry
        ret

.readOrWrite:
        mov     [bp+IDEPACK.bFeatures],ah       ; store protocol command

        mov     dl, byte [di+DPT.bSerialPortAndBaud]

; fall-through

;--------------------------------------------------------------------
; SerialCommand_OutputWithParameters_DeviceInDL
;   Parameters:
;       AH:     Protocol Command
;       DL:     Packed I/O port and baud rate
;       ES:SI:  Ptr to buffer (for data transfer commands)
;       SS:BP:  Ptr to IDEREGS_AND_INTPACK
;   Returns:
;       AH:     INT 13h Error Code
;       CF:     Cleared if success, Set if error
;   Corrupts registers:
;       AL, BX, CX, DX, (ES:SI for data transfer commands)
;--------------------------------------------------------------------
SerialCommand_OutputWithParameters_DeviceInDL:

        push    si
        push    di
        push    bp
        push    es

;
; Unpack I/O port and baud from DPT
;       Port to DX more or less for the remainder of the routine
;       Baud in CH until UART initialization is complete
;
        mov     cl, dl

        and     cl, SerialCommand_PackedPortAndBaud_BaudMask
        shl     cl, 1
        mov     ch, SerialCommand_UART_divisorLow_startingBaud
        shr     ch, cl
        adc     ch, 0

        and     dl, SerialCommand_PackedPortAndBaud_PortMask
        mov     dh, 0
        shl     dx, 1
        add     dx, SerialCommand_PackedPortAndBaud_StartingPort

;
; Buffer is referenced through ES:DI throughout, since we need to store faster than we read
;
        mov     di,si

        mov     al,[bp+IDEPACK.bSectorCount]

;
; Command byte and sector count live at the top of the stack, pop/push are used to access
;
        push    ax

;       cld     ; Shouldn't be needed. DF has already been cleared (line 24, Int13h.asm)

;----------------------------------------------------------------------
;
; Initialize UART
;
; We do this each time since DOS (at boot) or another program may have
; decided to reprogram the UART
;
        push    dx

        mov     al,83h
        add     dl,SerialCommand_UART_lineControl
        out     dx,al

        mov     al,ch
        pop     dx              ; divisor low
        out     dx,al

        xor     ax,ax
        inc     dx              ; divisor high
        push    dx
        out     dx,al

        mov     al,047h
        inc     dx              ;  fifo
        out     dx,al

        mov     al,03h
        inc     dx              ;  linecontrol
        out     dx,al

        mov     al,0bh
        inc     dx              ;  modemcontrol
        out     dx,al

        pop     dx              ; base, interrupts disabled
        xor     ax,ax
        out     dx,al
        dec     dx

;----------------------------------------------------------------------
;
; Send Command
;
; Sends first six bytes of IDEREGS_AND_INTPACK as the command
;
        call    Registers_NormalizeESDI

        push    es              ; save off real buffer location
        push    di

        mov     di,bp           ; point to IDEREGS for command dispatch;
        push    ss
        pop     es

        xor     si,si           ; initialize checksum for write
        dec     si
        mov     bp,si

        mov     bl,03h      ; writing 3 words

        call    SerialCommand_WriteProtocol

        pop     di              ; restore real buffer location
        pop     es

        pop     ax              ; load command byte (done before call to .nextSector on subsequent iterations)
        push    ax

;
; Top of the read/write loop, one iteration per sector
;
.nextSector:
        xor     si,si           ; initialize checksum for read or write
        dec     si
        mov     bp,si

        mov     bx,0100h

        shr     ah,1            ; command byte, are we doing a write?
        jnc     .readSector
        call    SerialCommand_WriteProtocol

        xor     bx,bx

.readSector:
        mov     cx,bx
        inc     cx

        mov     bl,dl           ; setup bl with proper values for read loop (bh comes later)

;----------------------------------------------------------------------
;
; Timeout
;
; During read, we first poll in a tight loop, interrupts off, for the next character to come in
; If that loop completes, then we assume there is a long delay involved, turn interrupts back on
; and wait for a given number of timer ticks to pass.
;
; To save code space, we use the contents of DL to decide which byte in the word to return for reading.
;
.readTimeout:
        push    cx
        xor     cx,cx
.readTimeoutLoop:
        push    dx
        or      dl,SerialCommand_UART_lineStatus
        in      al,dx
        pop     dx
        shr     al,1
        jc      .readTimeoutComplete
        loop    .readTimeoutLoop
        sti
        mov     bh,1
        call    SerialCommand_WaitAndPoll_Init
        cli
.readTimeoutComplete:
        mov     bh,bl
        or      bh,SerialCommand_UART_lineStatus

        pop     cx
        test    dl,1
        jz      .readByte1Ready
        jmp     .readByte2Ready

;----------------------------------------------------------------------------
;
; Read Block (without interrupts, used when there is a FIFO, high speed)
;
; NOTE: This loop is very time sensitive.  Literally, another instruction
; cannot be inserted into this loop without us falling behind at high
; speed (460.8K baud) on a 4.77Mhz 8088, making it hard to receive
; a full 512 byte block.
;
.readLoop:
        stosw                   ; store word in caller's data buffer

        add     bp, ax          ; update Fletcher's checksum
        adc     bp, 0
        add     si, bp
        adc     si, 0

        mov     dl,bh
        in      al,dx
        shr     al,1            ; data ready (byte 1)?
        mov     dl,bl           ; get ready to read data
        jnc     .readTimeout    ; nope not ready, update timeouts

;
; Entry point after initial timeout.  We enter here so that the checksum word
; is not stored (and is left in AX after the loop is complete).
;
.readByte1Ready:
        in      al, dx          ; read data byte 1

        mov     ah, al          ; store byte in ah for now

;
; note the placement of this reset of dl to bh, and that it is
; before the return, which is assymetric with where this is done
; above for byte 1.  The value of dl is used by the timeout routine
; to know which byte to return to (.read_byte1_ready or
; .read_byte2_ready)
;
        mov     dl,bh

        in      al,dx
        shr     al,1            ; data ready (byte 2)?
        jnc     .readTimeout
.readByte2Ready:
        mov     dl,bl
        in      al, dx          ; read data byte 2

        xchg    al, ah          ; ah was holding byte 1, reverse byte order

        loop    .readLoop

        sti                     ; interrupts back on ASAP, if we turned them off

;
; Compare checksums
;
        xor     bp,si
        cmp     ax,bp
        jnz     SerialCommand_OutputWithParameters_Error


;----------------------------------------------------------------------
;
; Clear read buffer
;
; In case there are extra characters or an error in the FIFO, clear it out.
; In theory the initialization of the UART registers above should have
; taken care of this, but I have seen cases where this is not true.
;
.clearBuffer:
        mov     dl,bh
        in      al,dx
        mov     dl,bl
        test    al,08fh
        jz      .clearBufferComplete
        shr     al,1
        in      al,dx
        jc      .clearBuffer    ; note CF from shr above
        jmp     SerialCommand_OutputWithParameters_Error

.clearBufferComplete:
        pop     ax              ; sector count and command byte
        dec     al              ; decrememnt sector count
        push    ax              ; save
        jz      SerialCommand_OutputWithParameters_ReturnCodeInALCF    ; CF clear from .clearBuffer test above

        cli                     ; interrupts back off for ACK byte to host
                                ; (host could start sending data immediately)
        out     dx,al           ; ACK with next sector number

        jmp     .nextSector     ; all is well, time for next sector

;---------------------------------------------------------------------------
;
; Cleanup, error reporting, and exit
;

;
; Used in situations where a call is underway, such as with SerialCommand_WaitAndPoll
;
SerialCommand_OutputWithParameters_ErrorAndPop2Words:
        pop     ax
        pop     ax

SerialCommand_OutputWithParameters_Error:
        stc
        mov     al,1

SerialCommand_OutputWithParameters_ReturnCodeInALCF:
        sti
        mov     ah,al

        pop     bp              ;  recover ax from stack, throw away

        pop     es
        pop     bp
        pop     di
        pop     si

        ret

;--------------------------------------------------------------------
; SerialCommand_WaitAndPoll
;
;   Parameters:
;       BH:     UART_LineStatus bit to test (20h for write, or 1h for read)
;       DX:     Port address (OK if already incremented to UART_lineStatus)
;       Stack:  2 words on the stack below the command/count word
;   Returns:
;       Returns when desired UART_LineStatus bit is cleared
;       Jumps directly to error exit if timeout elapses (and cleans up stack)
;   Corrupts registers:
;       CX, flags
;--------------------------------------------------------------------

SerialCommand_WaitAndPoll_SoftDelayTicks   EQU   20

ALIGN JUMP_ALIGN
SerialCommand_WaitAndPoll_Init:
        mov     cl,SerialCommand_WaitAndPoll_SoftDelayTicks
        call    Timer_InitializeTimeoutWithTicksInCL
; fall-through

SerialCommand_WaitAndPoll:
        call    Timer_SetCFifTimeout
        jc      SerialCommand_OutputWithParameters_ErrorAndPop2Words
        push    dx
        push    ax
        or      dl,SerialCommand_UART_lineStatus
        in      al,dx
        test    al,bh
        pop     ax
        pop     dx
        jz      SerialCommand_WaitAndPoll
; fall-through

SerialCommand_WaitAndPoll_Done:
        ret

;--------------------------------------------------------------------
; SerialCommand_WriteProtocol
;
;   Parameters:
;       ES:DI:  Ptr to buffer
;       BL:     Words to write (1-255, or 0=256)
;       BP/SI:  Initialized for Checksum (-1 in each)
;       DX:     I/O Port
;   Returns:
;       BP/SI:  Checksum for written bytes, compared against ACK from server in .readLoop
;   Corrupts registers:
;       AX, BX, CX, DI
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
SerialCommand_WriteProtocol:
        mov     bh,20h

.writeLoop:
        test    bh,1
        jnz     SerialCommand_WaitAndPoll_Done

        mov     ax,[es:di]      ; fetch next word
        inc     di
        inc     di

        add     bp,ax           ; update checksum
        adc     bp,0
        add     si,bp
        adc     si,0

.writeLoopChecksum:
        call    SerialCommand_WaitAndPoll_Init

        out     dx,al           ; output first byte

        call    SerialCommand_WaitAndPoll

        mov     al,ah           ; output second byte
        out     dx,al

        dec     bl
        jnz     .writeLoop

        inc     bh

        mov     ax,bp           ; merge checksum for possible write (last loop)
        xor     ax,si

        jmp     .writeLoopChecksum


; To return the port number and baud rate to the FinalizeDPT routine, we
; stuff the value in a "vendor" specific area of the 512-byte IdentifyDevice
; sector.
;
SerialCommand_IdentifyDevice_PackedPortAndBaud  equ     (157*2)

;--------------------------------------------------------------------
; SerialCommand_IdentifyDeviceToBufferInESSIwithDriveSelectByteInBH
;   Parameters:
;       BH:     Drive Select byte for Drive and Head Select Register
;       DS:     Segment to RAMVARS
;       ES:SI:  Ptr to buffer to receive 512-byte IDE Information
;       CS:BP:  Ptr to IDEVARS
;   Returns:
;       AH:     INT 13h Error Code
;       CF:     Cleared if success, Set if error
;   Corrupts registers:
;       AL, BL, CX, DX, SI, DI, ES
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
SerialCommand_IdentifyDeviceToBufferInESSIwithDriveSelectByteInBH:

        mov     dx,[cs:bp+IDEVARS.wPortCtrl]
        inc     dx
        dec     dx
        jz      SerialCommand_AutoSerial

; fall-through
SerialCommand_IdentifyDeviceInDL_DriveInBH:

        push    bp              ; setup fake IDEREGS_AND_INTPACK

        push    dx

        mov     cl,1            ; 1 sector to move
        push    cx

        mov     bl,0a0h         ; protocol command to ah and onto stack with bh
        mov     ah,bl

        push    bx

        mov     bp,sp

        call    SerialCommand_OutputWithParameters_DeviceInDL

        pop     bx

        pop     cx
        pop     dx

        pop     bp

; place packed port/baud in vendor area of packet, read by FinalizeDPT
        mov     byte [es:si+SerialCommand_IdentifyDevice_PackedPortAndBaud], dl

        ret

;----------------------------------------------------------------------
;
; SerialCommand_AutoSerial
;
; When the SerialAuto IDEVARS entry is used, scans the COM ports on the machine for a possible serial connection.
;

SerialCommand_ScanPortAddresses:  db  0b8h, 0f8h, 0bch, 0bah, 0fah, 0beh, 0feh, 0
; Corresponds to I/O port:             3f8,  2f8,  3e8,  2e8,  2f0,  3e0,  2e0,  260,  368,  268,  360,  270
; COM Assignments:                       1,    2,    3,    4,    5,    6,    7,    8,    9,   10,   11,   12

ALIGN JUMP_ALIGN
SerialCommand_AutoSerial:
        mov     di,SerialCommand_ScanPortAddresses-1

.nextPort:
        inc     di              ; load next port address
        mov     dl,[cs:di]

        mov     dh,0            ; shift from one byte to two
        eSHL_IM dx, 2
        jz      .exitNotFound

;
; Test for COM port presence, write to and read from registers
;
        push    dx
        add     dl,SerialCommand_UART_lineControl
        mov     al, 09ah
        out     dx, al
        in      al, dx
        pop     dx
        cmp     al, 09ah
        jnz     .nextPort

        mov     al, 0ch
        out     dx, al
        in      al, dx
        cmp     al, 0ch
        jnz     .nextPort

;
; Pack into dl, baud rate starts at 0
;
        add     dx,-(SerialCommand_PackedPortAndBaud_StartingPort)
        shr     dx,1

        jmp     .testFirstBaud

;
; Walk through 4 possible baud rates
;
.nextBaud:
        inc     dx
        test    dl,3
        jz      .nextPort

.testFirstBaud:
        call    SerialCommand_IdentifyDeviceInDL_DriveInBH
        jc      .nextBaud

        ret

.exitNotFound:
        stc
        mov     ah,1

        ret