📄 cstartup_flash.s
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b EndInitAic
#- Default Interrupt Handlers
AicData:
.long AIC_BASE /* AIC Base Address */
#------------------------------------------------------------------------------
#- Default Interrupt Handler
#------------------------------------------------------
#- These function are defined in the AT91 library. If you want to change this
#- you can redifine these function in your appication code
#------------------------------------------------------------------------------
.extern at91_default_fiq_handler
.extern at91_default_irq_handler
.extern at91_spurious_handler
PtDefaultHandler:
.long at91_default_fiq_handler
.long at91_default_irq_handler
.long at91_spurious_handler
EndInitAic:
#------------------------------------------------------------------------------
#- Setup Exception Vectors in Internal RAM before Remap
#------------------------------------------------------
#- That's important to perform this operation before Remap in order to guarantee
#- that the core has valid vectors at any time during the remap operation.
#- Note: There are only 5 offsets as the vectoring is used.
#------------------------------------------------------------------------------
#- Copy the ARM exception vectors
mov r8, #RAM_BASE_BOOT /* @ of the hard vector in internal RAM 0x300000 */
add r9, pc,#-(8+.-VectorTable) /* @ where to read values (relative) */
ldmia r9!, {r0-r7} /* read 8 vectors */
stmia r8!, {r0-r7} /* store them */
ldmia r9!, {r0-r4} /* read 5 absolute handler addresses */
stmia r8!, {r0-r4} /* store them */
#------------------------------------------------------------------------------
#- Initialise the Memory Controller
#----------------------------------
#- That's principaly the Remap Command. Actually, all the External Bus
#- Interface is configured with some instructions and the User Interface Image
#- as described above. The jump "mov pc, r12" could be unread as it is after
#- located after the Remap but actually it is thanks to the Arm core pipeline.
#- The IniTableEBI addressing must be relative .
#- The PtInitRemap must be absolute as the processor jumps at this address
#- immediatly after the Remap is performed.
#- Note also that the EBI base address is loaded in r11 by the "ldmia".
#------------------------------------------------------------------------------
#- Copy the Image of the Memory Controller
sub r10, pc,#(8+.-InitTableEBI) /* get the address of the chip select register image */
ldr r12, PtInitRemap /* get the real jump address ( after remap ) */
#- Copy Chip Select Register Image to Memory Controller and command remap
ldmia r10!, {r0-r9,r11} /* load the complete image and the EBI base */
stmia r11!, {r0-r9} /* store the complete image with the remap command */
#- Jump to ROM at its new address
mov pc, r12 /* jump and break the pipeline */
PtInitRemap:
.long InitRemap /* address where to jump after REMAP */
#------------------------------------------------------------------------------
#- The Reset Handler after Remap
#-------------------------------
#- From here, the code is executed from its link address, ie. 0x100 0000.
#------------------------------------------------------------------------------
InitRemap:
b InitRemap
#------------------------------------------------------------------------------
#- Stack Sizes Definition
#------------------------
#- Interrupt Stack requires 3 words x 8 priority level x 4 bytes when using
#- the vectoring. This assume that the IRQ_ENTRY/IRQ_EXIT macro are used.
#- The Interrupt Stack must be adjusted depending on the interrupt handlers.
#- Fast Interrupt is the same than Interrupt without priority level.
#- Other stacks are defined by default to save one word each.
#- The System stack size is not defined and is limited by the free internal
#- SRAM.
#- User stack size is not defined and is limited by the free external SRAM.
#------------------------------------------------------------------------------
.equ IRQ_STACK_SIZE, (3*8*4) /* 3 words per interrupt priority level */
.equ FIQ_STACK_SIZE, (3*4) /* 3 words */
.equ ABT_STACK_SIZE, (1*4) /* 1 word */
.equ UND_STACK_SIZE, (1*4) /* 1 word */
.equ SVC_STACK_SIZE, (20*4)
#------------------------------------------------------------------------------
#- Top of Stack Definition
#-------------------------
#- Fast Interrupt, Interrupt, Abort, Undefined and Supervisor Stack are located
#- at the top of internal memory in order to speed the exception handling
#- context saving and restoring.
#- User (Application, C) Stack is located at the top of the external memory.
#------------------------------------------------------------------------------
.equ TOP_EXCEPTION_STACK, RAM_LIMIT /* Defined in part */
#------------------------------------------------------------------------------
#- Setup the stack for each mode
#-------------------------------
ldr r0, =TOP_EXCEPTION_STACK
#;- Set up Fast Interrupt Mode and set FIQ Mode Stack
msr CPSR_c, #ARM_MODE_FIQ | I_BIT | F_BIT
mov r13, r0 /* Init stack FIQ */
sub r0, r0, #FIQ_STACK_SIZE
#- Set up Interrupt Mode and set IRQ Mode Stack
msr CPSR_c, #ARM_MODE_IRQ | I_BIT | F_BIT
mov r13, r0 /* Init stack IRQ */
sub r0, r0, #IRQ_STACK_SIZE
#- Set up Abort Mode and set Abort Mode Stack
msr CPSR_c, #ARM_MODE_ABORT | I_BIT | F_BIT
mov r13, r0 /* Init stack Abort */
sub r0, r0, #ABT_STACK_SIZE
#- Set up Undefined Instruction Mode and set Undef Mode Stack
msr CPSR_c, #ARM_MODE_UNDEF | I_BIT| F_BIT
mov r13, r0 /* Init stack Undef */
sub r0, r0, #UND_STACK_SIZE
#- Set up Supervisor Mode and set Supervisor Mode Stack
msr CPSR_c, #ARM_MODE_SVC | I_BIT | F_BIT
mov r13, r0 /* Init stack Sup */
sub r0, r0, #SVC_STACK_SIZE
#------------------------------------------------------------------------------
#- Setup Application Operating Mode and Enable the interrupts
#------------------------------------------------------------
#- System Mode is selected first and the stack is setup. This allows to prevent
#- any interrupt occurence while the User is not initialized. System Mode is
#- used as the interrupt enabling would be avoided from User Mode (CPSR cannot
#- be written while the core is in User Mode).
#------------------------------------------------------------------------------
msr CPSR_c, #ARM_MODE_USER /* set User mode */
mov r13, r0 /* Init stack User */
#------------------------------------------------------------------------------
#- 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.
#------------------------------------------------------------------------------
.extern Image_RO_Limit /* End of ROM code (=start of ROM data) */
.extern Image_RW_Base /* Base of RAM to initialise */
.extern Image_ZI_Base /* Base and limit of area */
.extern Image_ZI_Limit /* to zero initialise */
ldr r0, =Image_RO_Limit /* Get pointer to ROM data */
ldr r1, =Image_RW_Base /* and RAM copy */
ldr r3, =Image_ZI_Base /* Zero init base => top of initialised data */
cmp r0, r1 /* Check that they are different */
beq NoRW
LoopRw: cmp r1, r3 /* Copy init data */
ldrcc r2, [r0], #4
strcc r2, [r1], #4
bcc LoopRw
NoRW: ldr r1, =Image_ZI_Limit /* Top of zero init segment */
mov r2, #0
LoopZI: cmp r3, r1 /* Zero init */
strcc r2, [r3], #4
bcc LoopZI
#------------------------------------------------------------------------------
#- 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
#------------------------------------------------------------------------------
.extern 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
.global __gccmain
__gccmain:
mov pc, lr
# END
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