boot.s

嵌入式系统 EP93xx处理器

    // Return to the caller.
    //
    ldmfd   r13!, {r4, pc}

//****************************************************************************
//
// CopySdram copys the data receive via the serial port into the on-board
// SDRAM.
//
//****************************************************************************
CopySdram _LABEL_
    //
    // Save the link register to the stack.
    //
    stmfd   r13!, {r4-r7, lr}

    //
    // Send the command recieve data from the host.
    //
    mov     r0, _CONST_ 0x3c // '<'
    bl      SendChar

    //
    // Read the 4bytes of data, Get the file size.
    //
    bl      ReadLong
    mov     r6, r0

    mov     r0, _CONST_ 0x44 // 'D'
    bl      SendChar

    mov     r5, r11
    //mov     r6, _CONST_ 0x40000   

copy_loop _LABEL_
    //
    // Read the 4bytes of data.
    //
    bl      ReadLong

    //
    // Copy 4bytes word to SDRAM.
    //
    str     r0, [r5], _CONST_ 4
    
    //
    // Decrement the count of bytes.
    //
    subs     r6, r6, _CONST_ 4
    bne     copy_loop

    //
    // Send the command terminate transfer.
    //
    mov     r0, _CONST_ 0x3e // '<'
    bl      SendChar
    
    ldmfd   r13!, {r4-r7, pc}
       
//****************************************************************************
//
// The boot code entry.
//
//****************************************************************************
SetUp _LABEL_
    //
    // Detect the nSDCS3 sync boot base address.
    //
    ldr     r11, =0x00000000
    
    //
    // Try a 32-bit wide configuration of SDRAM.
    //
    ldr     r0, =0x00210028
    ldr     r1, =0x00400000
    orr     r2, r11, _CONST_ 0x00008800
    ldr     r3, =0x80060000
    str     r0, [r3, _CONST_ 0x001c]
    bl      SdramConfig

    //
    // Test the SDRAM.
    //
    mov     r0, r11
    bl      SdramDetect
    cmp     r0, _CONST_ 0x00000000
    beq     SdramOk

    //
    // Try a 16-bit wide configuration of SDRAM.
    //
    ldr     r0, =0x0021002c
    ldr     r1, =0x00200000
    orr     r2, r11, _CONST_ 0x00004600
    ldr     r3, =0x80060000
    str     r0, [r3, _CONST_ 0x001c]
    bl      SdramConfig

    //
    // Test the SDRAM.
    //
    mov     r0, r11
    bl      SdramDetect
    cmp     r0, _CONST_ 0x00000000
    beq     SdramOk
        
    //
    // Detect the nSDCS0 base address.
    //
    ldr     r11, =0xc0000000

    //
    // Try a 32-bit wide configuration of SDRAM.
    //
    ldr     r0, =0x00210028
    ldr     r1, =0x00400000
    orr     r2, r11, _CONST_ 0x00008800
    ldr     r3, =0x80060000
    str     r0, [r3, _CONST_ 0x0010]
    bl      SdramConfig

    //
    // Test the SDRAM.
    //
    mov     r0, r11
    bl      SdramDetect
    cmp     r0, _CONST_ 0x00000000
    beq     SdramOk

    //
    // Try a 16-bit wide configuration of SDRAM.
    //
    ldr     r0, =0x0021002c
    ldr     r1, =0x00200000
    orr     r2, r11, _CONST_ 0x00004600
    ldr     r3, =0x80060000
    str     r0, [r3, _CONST_ 0x0010]
    bl      SdramConfig

    //
    // Test the SDRAM.
    //
    mov     r0, r11
    bl      SdramDetect
    cmp     r0, _CONST_ 0x00000000
    beq     SdramOk

    //
    // Detect the nSDCS1 base address.
    //
    ldr     r11, =0xd0000000

    //
    // Try a 32-bit wide configuration of SDRAM.
    //
    ldr     r0, =0x00210028
    ldr     r1, =0x00400000
    orr     r2, r11, _CONST_ 0x00008800
    ldr     r3, =0x80060000
    str     r0, [r3, _CONST_ 0x0014]
    bl      SdramConfig

    //
    // Test the SDRAM.
    //
    mov     r0, r11
    bl      SdramDetect
    cmp     r0, _CONST_ 0x00000000
    beq     SdramOk

    //
    // Try a 16-bit wide configuration of SDRAM.
    //
    ldr     r0, =0x0021002c
    ldr     r1, =0x00200000
    orr     r2, r11, _CONST_ 0x00004600
    ldr     r3, =0x80060000
    str     r0, [r3, _CONST_ 0x0014]
    bl      SdramConfig

    //
    // Test the SDRAM.
    //
    mov     r0, r11
    bl      SdramDetect
    cmp     r0, _CONST_ 0x00000000
    beq     SdramOk

    //
    // Detect the nSDCS2 base address.
    //
    ldr     r11, =0xe0000000

    //
    // Try a 32-bit wide configuration of SDRAM.
    //
    ldr     r0, =0x00210028
    ldr     r1, =0x00400000
    orr     r2, r11, _CONST_ 0x00008800
    ldr     r3, =0x80060000
    str     r0, [r3, _CONST_ 0x0018]
    bl      SdramConfig

    //
    // Test the SDRAM.
    //
    mov     r0, r11
    bl      SdramDetect
    cmp     r0, _CONST_ 0x00000000
    beq     SdramOk

    //
    // Try a 16-bit wide configuration of SDRAM.
    //
    ldr     r0, =0x0021002c
    ldr     r1, =0x00200000
    orr     r2, r11, _CONST_ 0x00004600
    ldr     r3, =0x80060000
    str     r0, [r3, _CONST_ 0x0018]
    bl      SdramConfig

    //
    // Test the SDRAM.
    //
    mov     r0, r11
    bl      SdramDetect
    cmp     r0, _CONST_ 0x00000000
    beq     SdramOk

    //
    // Detect the nSDCS3 async boot base address.
    //
    ldr     r11, =0xf0000000

    //
    // Try a 32-bit wide configuration of SDRAM.
    //
    ldr     r0, =0x00210028
    ldr     r1, =0x00400000
    orr     r2, r11, _CONST_ 0x00008800
    ldr     r3, =0x80060000
    str     r0, [r3, _CONST_ 0x001c]
    bl      SdramConfig

    //
    // Test the SDRAM.
    //
    mov     r0, r11
    bl      SdramDetect
    cmp     r0, _CONST_ 0x00000000
    beq     SdramOk

    //
    // Try a 16-bit wide configuration of SDRAM.
    //
    ldr     r0, =0x0021002c
    ldr     r1, =0x00200000
    orr     r2, r11, _CONST_ 0x00004600
    ldr     r3, =0x80060000
    str     r0, [r3, _CONST_ 0x001c]
    bl      SdramConfig

    //
    // Test the SDRAM.
    //
    mov     r0, r11
    bl      SdramDetect
    cmp     r0, _CONST_ 0x00000000
    beq     SdramOk

    //
    // Send a 'X' to the host to indicate that we did not find SDRAM.
    //
    mov     r0, _CONST_ 0x58 // 'X'
    bl      SendChar

    //
    // Loop forever.
    //
    b       .

    //
    // Save the SDRAM base address to 0x80014780
    //
SdramOk _LABEL_
    ldr     r1, =0x80014780
    str     r11, [r1]

    //
    // Loop forever reading commands from the host and performing them.
    //
loop _LABEL_
        //
        // Write the command prompt to the host.
        //
        mov     r0, _CONST_ 0x3f // '?'
        bl      SendChar

        //
        // Read a command from the host.
        //
        bl      ReceiveChar

        //
        // Determine how to handle this command.  Is this a 'B'?
        //
        cmp     r0, _CONST_ 0x42 // 'B'
        bne     loop1

            //
            // Change the baud rate of the serial port.
            //
            bl      SetBaud
            b       loop

       //
       // Is this a 'C'?
       //
loop1 _LABEL_
       cmp     r0, _CONST_ 0x43 // 'C'
       bne     loop

           //
           // Copy data into the on-board SDRAM.
           //
           bl      CopySdram
           
           //
           // Switch to SDRAM to run second boot.
           //
           ldr     r1, =0x80014780
           ldr     r11, [r1]
           mov     pc, r11
           nop
           
       b       loop

//****************************************************************************
//
// The zero-initialized read-write data used by the application.
//
//****************************************************************************
    _BSS_

//****************************************************************************
//
// A buffer to contain 1K bytes of data read from the serial port that is to be
// programmed into the FLASH.
//
//****************************************************************************
    _SPACE_ 0x400
    
Stack _LABEL_

    _END_