cstartup.s

ARM入门的好帮手.包含了从简单到相对较复杂的程序.

;------------------------------------------------------------------------------
;-         ATMEL Microcontroller Software Support  -  ROUSSET  -
;------------------------------------------------------------------------------
; The software is delivered "AS IS" without warranty or condition of any
; kind, either express, implied or statutory. This includes without
; limitation any warranty or condition with respect to merchantability or
; fitness for any particular purpose, or against the infringements of
; intellectual property rights of others.
;-----------------------------------------------------------------------------
;- File source          : cstartup.s
;- Object               : C startup choice for EB42
;-
;- 1.0 17/07/00  PF     : Creation
;- 1.1 10/06/01  PF     : New cstartup
;------------------------------------------------------------------------------
                 INCLUDE     ../../targets/eb42/eb42.inc

;------------------------------------------------------------------------------
;               Angel Rom Monitor Method
;- Preprocessor Flag can be set : SEMIHOSTING
;------------------------------------------------------------------------------
                IF  :DEF:AT91_DEBUG_ANGEL       
                INCLUDE     ..\cstartup_angel.s

;----------------------------------------------------------------------
; Call __low_level_init to perform initialization before initializing
; AIC and calling main.
; Diasable all peripherial clock
;----------------------------------------------------------------------
__low_level_init
                mov         pc,r14              ; Return
                ENDIF                           ; AT91_DEBUG_ANGEL }

;------------------------------------------------------------------------------
;               ICE or Sram Method
;- Preprocessor Flag can be set : SEMIHOSTING
;------------------------------------------------------------------------------

                IF  :DEF:AT91_DEBUG_ICE         ; {
                INCLUDE     ..\cstartup_ice.s
;----------------------------------------------------------------------
; Call __low_level_init to perform initialization before initializing
; AIC and calling main.
; Diasable all peripherial clock
;----------------------------------------------------------------------
__low_level_init

                mvn         r0,#0               ; R0<- 0xFFFFFFFF
                ldr         r1,=PMC_BASE        ; Get Power saving configuartion
                str         r0,[r1,#PMC_PCDR]   ; Diasable all peripherial clock
                mov         pc,r14              ; Return                    

                ENDIF                           ; AT91_DEBUG_ICE  }

;------------------------------------------------------------------------------
;               Flash Method
;------------------------------------------------------------------------------

                IF  :DEF:AT91_DEBUG_NONE        ; {
                INCLUDE     ..\cstartup_flash.s
;----------------------------------------------------------------------
; Call __low_level_init to perform initialization before initializing
; AIC and calling main.
; Pll Initialization 
;----------------------------------------------------------------------
__low_level_init

;---------------------------------------------------------------------------
;               - Power Management Controller Configuration -              -
;---------------------------------------------------------------------------
; At reset, the AT91M42800 runs from the Slow Clock Oscillator @ 32,768Khz.
; The PLLA is uses to run @ 32,768Mhz --> 32,768Khz*(999 + 1)
;  

;- Disable External Watchdog assertion      -
;--------------------------------------------
        ldr r0, =0x0             
        ldr r1, =ST_BASE
        str r0, [r1, #ST_WDMR]       ; Disable the WatchDog Timer

;- Set up the Clock frequency to run at 32,768 Mhz with PLLA
;-------------------------------------------------------------
                ldr     r0, =0xC503E700             ; PLLCOUNT = 197 (6ms, 0xC5), MUL=999, PLLA
                ldr     r1, =PMC_BASE               ; Get the PMC Base Address
                str     r0, [r1, #PMC_CGMR]         ; Store the configuration of the Clock Generator

;- Reading the PMC Status Register to detect when the PLLA is stabilized
;-----------------------------------------------------------------------
                mov     r4, #PMC_PLL_LOCK       ; PLL Lock bit in PMC_SR
PllLoop
                ldr     r2, [r1, #PMC_SR]
                cmp     r2, r4
                bne     PllLoop

;- Commuting from Slow Clock (32,768Khz) to PLLA (32,768Mhz)
;-----------------------------------------------------------
                ldr     r0, =0xC503E790             ; PLLCOUNT = 197 (6ms, 0xC5), MUL=999, CSS= PLL, PLLA
                str     r0, [r1, #PMC_CGMR]         ; Store the configuration of the Clock Generator
                            

;---------------------------------------------------------
;- Now the Master clock is the output of PLLA @ 32,768MHz -
;---------------------------------------------------------
                
                
                
                mov         pc,r14              ; Return
                ENDIF                           ; AT91_DEBUG_NONE }

 

        END