MODULE ?cstartup
;; Forward declaration of sections.
SECTION IRQ_STACK:DATA:NOROOT(2)
SECTION CSTACK:DATA:NOROOT(3)
//------------------------------------------------------------------------------
// Headers
//------------------------------------------------------------------------------
#define __ASSEMBLY__
#include "board.h"
//------------------------------------------------------------------------------
// Definitions
//------------------------------------------------------------------------------
#define ARM_MODE_ABT 0x17
#define ARM_MODE_FIQ 0x11
#define ARM_MODE_IRQ 0x12
#define ARM_MODE_SVC 0x13
#define ARM_MODE_SYS 0x1F
#define I_BIT 0x80
#define F_BIT 0x40
//------------------------------------------------------------------------------
// Startup routine
//------------------------------------------------------------------------------
/*
Exception vectors
*/
SECTION .vectors:CODE:NOROOT(2)
PUBLIC resetVector
PUBLIC irqHandler
EXTERN Undefined_Handler
EXTERN SWI_Handler
EXTERN Prefetch_Handler
EXTERN Abort_Handler
EXTERN FIQ_Handler
ARM
__iar_init$$done: ; The interrupt vector is not needed
; until after copy initialization is done
resetVector:
; All default exception handlers (except reset) are
; defined as weak symbol definitions.
; If a handler is defined by the application it will take precedence.
LDR pc, =resetHandler ; Reset
LDR pc, Undefined_Addr ; Undefined instructions
LDR pc, SWI_Addr ; Software interrupt (SWI/SYS)
LDR pc, Prefetch_Addr ; Prefetch abort
LDR pc, Abort_Addr ; Data abort
B . ; RESERVED
LDR pc, =irqHandler ; IRQ
LDR pc, FIQ_Addr ; FIQ
Undefined_Addr: DCD Undefined_Handler
SWI_Addr: DCD SWI_Handler
Prefetch_Addr: DCD Prefetch_Handler
Abort_Addr: DCD Abort_Handler
FIQ_Addr: DCD FIQ_Handler
/*
Handles incoming interrupt requests by branching to the corresponding
handler, as defined in the AIC. Supports interrupt nesting.
*/
irqHandler:
/* Save interrupt context on the stack to allow nesting */
SUB lr, lr, #4
STMFD {lr}
MRS lr, SPSR
STMFD {r0, lr}
/* Write in the IVR to support Protect Mode */
LDR lr, =AT91C_BASE_AIC
LDR r0, [r14, #AIC_IVR]
STR lr, [r14, #AIC_IVR]
/* Branch to interrupt handler in Supervisor mode */
MSR CPSR_c, #ARM_MODE_SYS
STMFD {r1-r3, r4, r12, lr}
MOV lr, pc
BX r0
LDMIA {r1-r3, r4, r12, lr}
MSR CPSR_c, #ARM_MODE_IRQ | I_BIT
/* Acknowledge interrupt */
LDR lr, =AT91C_BASE_AIC
STR lr, [r14, #AIC_EOICR]
/* Restore interrupt context and branch back to calling code */
LDMIA {r0, lr}
MSR SPSR_cxsf, lr
LDMIA {pc}^
/*
After a reset, execution starts here, the mode is ARM, supervisor
with interrupts disabled.
Initializes the chip and branches to the main() function.
*/
SECTION .cstartup:CODE:NOROOT(2)
PUBLIC resetHandler
EXTERN LowLevelInit
EXTERN ?main
REQUIRE resetVector
ARM
resetHandler:
/* Set pc to actual code location (i.e. not in remap zone) */
LDR pc, =label
/* Perform low-level initialization of the chip using LowLevelInit() */
label:
LDR r0, =LowLevelInit
LDR r4, =SFE(CSTACK)
MOV sp, r4
MOV lr, pc
BX r0
/* Set up the interrupt stack pointer. */
MSR cpsr_c, #ARM_MODE_IRQ | I_BIT | F_BIT ; Change the mode
LDR sp, =SFE(IRQ_STACK)
/* Set up the SYS stack pointer. */
MSR cpsr_c, #ARM_MODE_SYS | F_BIT ; Change the mode
LDR sp, =SFE(CSTACK)
/* Branch to main() */
LDR r0, =?main
MOV lr, pc
BX r0
/* Loop indefinitely when program is finished */
loop4:
B loop4
END
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