;------------------------------------------------------------------------------
;-         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_boot.arm
;- Object               : Generic CStartup
;- Compilation flag     : None
;-
;- 1.0 23/10/02 	FB  : Creation ARM ADS
;------------------------------------------------------------------------------

	INCLUDE   AT91RM9200.inc

;--------------------------------
;- ARM Core Mode and Status Bits
;--------------------------------

ARM_MODE_USER           EQU     0x10
ARM_MODE_FIQ            EQU     0x11
ARM_MODE_IRQ            EQU     0x12
ARM_MODE_SVC            EQU     0x13
ARM_MODE_ABORT          EQU     0x17
ARM_MODE_UNDEF          EQU     0x1B
ARM_MODE_SYS            EQU     0x1F

I_BIT                   EQU     0x80
F_BIT                   EQU     0x40
T_BIT                   EQU     0x20

;------------------------------------------------------------------------------
;- Stack Area Definition
;-----------------------
;- 
;------------------------------------------------------------------------------
		AREA        |C$$stack|, DATA
 	               
;- IRQ stack definition                              
AT91_IRQ_Stack_End    DCD   0x55AA55AA
                     SPACE (IRQ_STACK_SIZE - 4)
AT91_IRQ_Stack_Begin  EQU   (AT91_IRQ_Stack_End + (IRQ_STACK_SIZE - 4))

;- FIQ stack definition
AT91_FIQ_Stack_End   DCD   0x55AA55AA
                    SPACE (FIQ_STACK_SIZE - 4)
AT91_FIQ_Stack_Begin EQU   (AT91_FIQ_Stack_End + (FIQ_STACK_SIZE - 4))

;- ABORT stack definition
AT91_ABT_Stack_End   DCD   0x55AA55AA
                    SPACE (ABT_STACK_SIZE - 4)
AT91_ABT_Stack_Begin EQU   (AT91_ABT_Stack_End + (ABT_STACK_SIZE - 4))

;- UNDEF stack definition
AT91_UND_Stack_End   DCD   0x55AA55AA
                    SPACE (UND_STACK_SIZE - 4)
AT91_UND_Stack_Begin EQU   (AT91_UND_Stack_End + (UND_STACK_SIZE - 4))

;- SVC stack definition
AT91_SVC_Stack_End   DCD   0x55AA55AA
                    SPACE (SVC_STACK_SIZE-4)
AT91_SVC_Stack_Begin EQU   (AT91_SVC_Stack_End + (SVC_STACK_SIZE-4))

;- USER and SYSTEM stack definition
AT91_USER_Stack_End   DCD   0x55AA55AA
                      SPACE (USER_STACK_SIZE-4)
AT91_USER_Stack_Begin EQU   (AT91_USER_Stack_End + (USER_STACK_SIZE-4))

	EXPORT AT91_IRQ_Stack_End
	EXPORT AT91_IRQ_Stack_Begin
	EXPORT AT91_FIQ_Stack_End
	EXPORT AT91_FIQ_Stack_Begin
	EXPORT AT91_ABT_Stack_End
	EXPORT AT91_ABT_Stack_Begin
	EXPORT AT91_UND_Stack_End
	EXPORT AT91_UND_Stack_Begin
	EXPORT AT91_SVC_Stack_End
	EXPORT AT91_SVC_Stack_Begin
	EXPORT AT91_USER_Stack_End
	EXPORT AT91_USER_Stack_Begin


;------------------------------------------------------------------------------
;- Area Definition
;-----------------
;- Must be defined as function to put first in the code as it must be mapped
;- at offset 0 of the flash EBI_CSR0, ie. at address 0 before remap.
;------------------------------------------------------------------------------
                AREA        reset, CODE, READONLY


;	IMPORT __use_no_semihosting_swi
;------------------------------------------------------------------------------
;- Define the entry point
;------------------------

	EXPORT	__ENTRY
__ENTRY

;------------------------------------------------------------------------------
;- Exception vectors ( before Remap )
;------------------------------------
;- These vectors are read at address 0.
;- They absolutely requires to be in relative addresssing mode in order to 
;- guarantee a valid jump. For the moment, all are just looping (what may be 
;- dangerous in a final system). If an exception occurs before remap, this 
;- would result in an infinite loop. 
;------------------------------------------------------------------------------
                B           InitReset       	; reset
undefvec
                B           undefvec        	; Undefined Instruction
swivec
                B           swivec          	; Software Interrupt
pabtvec
                B           pabtvec         	; Prefetch Abort
dabtvec 
                B           dabtvec         	; Data Abort
rsvdvec
                B           rsvdvec         	; reserved
irqvec
                ldr         pc, [pc,#-0xF20]    ; IRQ : read the AIC
fiqvec
                B           fiqvec          	; FIQ


;-------------------
;- The reset handler
;-------------------
InitReset

;------------------------------------------------------------------------------
;-PMC initialisation : Enable the Main Oscillator
;------------------------------------------------------------------------------
;-Slow clock mode init
;-After reset, only the 32KHz oscillator is enabled. 
;-The ARM7TDMI or ARM9 runs the first instructions at 32768Hz <=> Slow Clock.
;-The processor clock and master clock are enabled at slow clock.
;-All the peripheral clocks are disabled.
;-The main oscillator is disabled.
;------------------------------------------------------------------------------

;------------------------------------------------------------------------------
;Step 0a.
;------------------------------------------------------------------------------
;-After reset, Slow Clock is normally selected
;-But in case of a boot already started, re-selection of Slow Clock
;-In two steps because of constraints of the Master Clock selection sequence
;-Can be cleared if the project is used for a boot execution
;------------------------------------------------------------------------------
	ldr     r1, = AT91C_BASE_PMC	; Get the PMC Base Address

;------------------------------------------------------------------------------
;-Write in the MCKR dirty value concerning the clock selection CSS then overwrite it in a second sequence
;------------------------------------------------------------------------------
;-Master Clock Register PMC_MCKR : "dirty CSS" is selected
	ldr 	r0, = AT91C_PMC_CSS_PLLB_CLK
	str     r0, [r1, #PMC_MCKR]

;- Reading the PMC Status register to detect when the Master Clock is commuted
                mov     r4, #0x8
MCKR_Loop
                ldr     r3, [r1, #PMC_SR]
                and     r3, r4, r3
                cmp     r3, #0x8
                bne     MCKR_Loop

;------------------------------------------------------------------------------
;-Second sequence
;------------------------------------------------------------------------------
;-Master Clock Register PMC_MCKR : Slow Clock is selected
	ldr 	r0, = AT91C_PMC_CSS_SLOW_CLK :OR:AT91C_PMC_PRES_CLK
	str     r0, [r1, #PMC_MCKR]

;- Reading the PMC Status register to detect when the Master Clock is commuted
                mov     r4, #0x8
MCKR_Loop2
                ldr     r3, [r1, #PMC_SR]
                and     r3, r4, r3
                cmp     r3, #0x8
                bne     MCKR_Loop2
                	
;------------------------------------------------------------------------------
;Step 0b.
;------------------------------------------------------------------------------
;-After reset,PLLs are disabled
;-But in case of a boot already started, PLLs are turned off
;-Can be cleared if the project is used for a boot execution
;------------------------------------------------------------------------------
	ldr     r1, = AT91C_BASE_CKGR	; Get the CKGR Base Address

;-Master Clock Register PMC_PLLAR : Turned off PLLA
	ldr 	r0, = AT91C_CKGR_DIVA_0
	str     r0, [r1, #CKGR_PLLAR]

;-Master Clock Register PMC_PLLBR : Turned off PLLB
	ldr 	r0, = AT91C_CKGR_DIVB_0
	str     r0, [r1, #CKGR_PLLBR]

;------------------------------------------------------------------------------
;Step 1.
;------------------------------------------------------------------------------
;-Enabling the Main Oscillator
;-Normally First instruction in PMC initialisation
;------------------------------------------------------------------------------
;-Main oscillator Enable register	APMC_MOR : Enable main oscillator , OSCOUNT = 0xFF
	ldr 	r0, = AT91C_CKGR_MOSCEN:OR:AT91C_CKGR_OSCOUNT
	str     r0, [r1, #CKGR_MOR]

;------------------------------------------------------------------------------
;- Setup the stack for each mode
;-------------------------
;- The processor will remain in the last initialized mode.
;------------------------------------------------------------------------------

;- Load the stack base addresses
	add     r0, pc,#-(8+.-StackData)  ; @ where to read values (relative)
	ldmia   r0, {r1-r6}

;- Set up Supervisor Mode and set SVC Mode Stack
	msr     cpsr_c, #ARM_MODE_SVC:OR:I_BIT:OR:F_BIT
	bic     r1, r1, #3                  ; Insure word alignement
	mov     sp, r1                      ; Init stack SYS
	
;- Set up Interrupt Mode and set IRQ Mode Stack
	msr     CPSR_c, #ARM_MODE_IRQ:OR:I_BIT:OR:F_BIT
	bic     r2, r2, #3                  ; Insure word alignement
	mov     sp, r2                      ; Init stack IRQ

;- Set up Fast Interrupt Mode and set FIQ Mode Stack
	msr     CPSR_c, #ARM_MODE_FIQ:OR:I_BIT:OR:F_BIT
	bic     r3, r3, #3                  ; Insure word alignement
	mov     sp, r3                      ; Init stack FIQ

;- Set up Abort Mode and set Abort Mode Stack
	msr     CPSR_c, #ARM_MODE_ABORT:OR:I_BIT:OR:F_BIT
	bic     r4, r4, #3                  ; Insure word alignement
	mov     sp, r4                      ; Init stack Abort

;- Set up Undefined Instruction Mode and set Undef Mode Stack
	msr     CPSR_c, #ARM_MODE_UNDEF:OR:I_BIT:OR:F_BIT
	bic     r5, r5, #3                  ; Insure word alignement
	mov     sp, r5                      ; Init stack Undef

;- Set up user Mode and set Undef Mode Stack
	msr     CPSR_c, #ARM_MODE_SYS:OR:I_BIT:OR:F_BIT
	bic     r6, r6, #3                  ; Insure word alignement
	mov     sp, r6                      ; Init stack Undef

	b       EndInitStack
	
StackData
	DCD     AT91_SVC_Stack_Begin
	DCD     AT91_IRQ_Stack_Begin
	DCD     AT91_FIQ_Stack_Begin
	DCD     AT91_ABT_Stack_Begin
	DCD     AT91_UND_Stack_Begin
	DCD     AT91_USER_Stack_Begin	
EndInitStack

;------------------------------------------------------------------------------
;-Low level Init (PMC, AIC, EBI, ....)
;------------------------------------------------------------------------------

;- Add loop to compensate Main Oscillator startup time	 
	ldr 	r0, =0x00000010
LoopOsc
	subs    r0, r0, #1              
	bhi     LoopOsc

	IMPORT    AT91F_LowLevelInit
	
	ldr       r0, = AT91F_LowLevelInit
	mov       lr, pc
	bx        r0

;----------------------------------------
; Read/modify/write CP15 control register 
;----------------------------------------
    MRC     p15, 0, r0, c1, c0,0 ; read cp15 control registre (cp15 r1) in r0
    ldr     r3, =0xC0000080      ; Reset bit :Little Endian end fast bus mode
    ldr     r4, =0xC0000000      ; Set bit :Asynchronous clock mode, Not Fast Bus
    BIC     r0, r0, r3             
    ORR     r0, r0, r4             
    MCR     p15, 0, r0, c1, c0,0 ; write r0 in cp15 control registre (cp15 r1)

;------------------------------------------------------------------------------
;- Initialise C variables
;------------------------
;- Following labels are automatically generated by the linker. 
;- RO: Read-only = the code
;- RW: Read Write = the data pre-initialized and zero-initialized.
;- ZI: Zero-Initialized.
;- Pre-initialization values are located after the code area in the image.
;- Zero-initialized datas are mapped after the pre-initialized.
;- Note on the Data position : 
;- If using the ARMSDT, when no -rw-base option is used for the linker, the 
;- data area is mapped after the code. You can map the data either in internal
;- SRAM ( -rw-base=0x40 or 0x34) or in external SRAM ( -rw-base=0x2000000 ).
;- Note also that to improve the code density, the pre_initialized data must 
;- be limited to a minimum.
;------------------------------------------------------------------------------

	add     r2, pc,#-(8+.-CInitData)  ; @ where to read values (relative)
	ldmia   r2, {r0, r1, r3, r4}
	
	cmp         r0, r1                  ; Check that they are different
	beq         EndRW
LoopRW	
	cmp         r1, r3                  ; Copy init data
	ldrcc       r2, [r0], #4
	strcc       r2, [r1], #4
	bcc         LoopRW
EndRW

	mov         r2, #0
LoopZI	
	cmp         r3, r4                  ; Zero init
	strcc       r2, [r3], #4
	bcc         LoopZI
 
	b           EndInitC
                
CInitData
 	IMPORT      |Image$$RO$$Limit|      ; End of ROM code (=start of ROM data)
	IMPORT      |Image$$RW$$Base|       ; Base of RAM to initialise
	IMPORT      |Image$$ZI$$Base|       ; Base and limit of area
	IMPORT      |Image$$ZI$$Limit|      ; Top of zero init segment
	
	DCD     |Image$$RO$$Limit|      ; End of ROM code (=start of ROM data)
 	DCD     |Image$$RW$$Base|       ; Base of RAM to initialise
 	DCD     |Image$$ZI$$Base|       ; Base and limit of area
 	DCD     |Image$$ZI$$Limit|      ; Top of zero init segment
EndInitC

  
;------------------------------------------------------------------------------
;- Branch on C code Main function (with interworking)
;----------------------------------------------------
;- Branch must be performed by an interworking call as either an ARM or Thumb 
;- main C function must be supported. This makes the code not position-
;- independant. A Branch with link would generate errors 
;------------------------------------------------------------------------------
	IMPORT      main
_main
__main
	EXPORT    _main
	EXPORT    __main
	ldr       r0, =main
	mov       lr, pc
	bx        r0

;------------------------------------------------------------------------------
;- Loop for ever
;---------------
;- End of application. Normally, never occur.
;- Could jump on Software Reset ( B 0x0 ).
;------------------------------------------------------------------------------
End
	b           End
	
	
	
            END