📄 os_cpu_a.s
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; e) Restore the new task''s context from the new task''s stack
; f) Return to new task''s code
;
; 3) Upon entry:
; OSTCBCur points to the OS_TCB of the task to suspend
; OSTCBHighRdy points to the OS_TCB of the task to resume
;*********************************************************************************************************
;??? RSEG CODE:CODE:NOROOT(2)
CODE32
OSIntCtxSw
BL OSTaskSwHook ; OSTaskSwHook();
LDR R4,addr_OSPrioCur ; OSPrioCur = OSPrioHighRdy
LDR R5,addr_OSPrioHighRdy
LDRB R6,[R5]
STRB R6,[R4]
LDR R4,addr_OSTCBCur ; OSTCBCur = OSTCBHighRdy;
LDR R6,addr_OSTCBHighRdy
LDR R6,[R6]
STR R6,[R4]
LDR SP,[R6] ; SP = OSTCBHighRdy->OSTCBStkPtr;
; RESTORE NEW TASK''S CONTEXT
LDR R4, [SP], #4 ; pop new task''s CPSR
MSR CPSR_cxsf, R4
LDR R0, [SP], #4 ; pop new task''s context
LDR R1, [SP], #4
LDR R2, [SP], #4
LDR R3, [SP], #4
LDR R4, [SP], #4
LDR R5, [SP], #4
LDR R6, [SP], #4
LDR R7, [SP], #4
LDR R8, [SP], #4
LDR R9, [SP], #4
LDR R10, [SP], #4
LDR R11, [SP], #4
LDR R12, [SP], #4
LDR LR, [SP], #4
LDR PC, [SP], #4
;*********************************************************************************************************
; IRQ Interrupt Service Routine
;*********************************************************************************************************
;??? RSEG CODE:CODE:NOROOT(2)
AREA irq_isr,CODE,READONLY
; CODE32
OS_CPU_IRQ_ISR
STR R3, [SP, #-4]! ; PUSH WORKING REGISTERS ONTO IRQ STACK
STR R2, [SP, #-4]!
STR R1, [SP, #-4]!
MOV R1, SP ; Save IRQ stack pointer
ADD SP, SP,#12 ; Adjust IRQ stack pointer
SUB R2, LR,#4 ; Adjust PC for return address to task
MRS R3, SPSR ; Copy SPSR (i.e. interrupted task''s CPSR) to R3
MSR CPSR_c, #(NO_INT | SYS32_MODE) ; Change to SYS mode
; SAVE TASK''S CONTEXT ONTO TASK''S STACK
STR R2, [SP, #-4]! ; Push task''s Return PC
STR LR, [SP, #-4]! ; Push task''s LR
STR R12, [SP, #-4]! ; Push task''s R12-R4
STR R11, [SP, #-4]!
STR R10, [SP, #-4]!
STR R9, [SP, #-4]!
STR R8, [SP, #-4]!
STR R7, [SP, #-4]!
STR R6, [SP, #-4]!
STR R5, [SP, #-4]!
STR R4, [SP, #-4]!
LDR R4, [R1], #4 ; Move task''s R1-R3 from IRQ stack to SYS stack
LDR R5, [R1], #4
LDR R6, [R1], #4
STR R6, [SP, #-4]!
STR R5, [SP, #-4]!
STR R4, [SP, #-4]!
STR R0, [SP, #-4]! ; Push task''s R0 onto task''s stack
STR R3, [SP, #-4]! ; Push task''s CPSR (i.e. IRQ''s SPSR)
; HANDLE NESTING COUNTER
LDR R0, addr_OSIntNesting ; OSIntNesting++;
LDRB R1, [R0]
ADD R1, R1,#1
STRB R1, [R0]
CMP R1, #1 ; if (OSIntNesting == 1) {
BNE OS_CPU_IRQ_ISR_1
LDR R4, addr_OSTCBCur ; OSTCBCur->OSTCBStkPtr = SP
LDR R5, [R4]
STR SP, [R5] ; }
OS_CPU_IRQ_ISR_1
MSR CPSR_c, #(NO_INT | IRQ32_MODE) ; Change to IRQ mode (to use the IRQ stack to handle interrupt)
BL OS_CPU_IRQ_ISR_Handler ; OS_CPU_IRQ_ISR_Handler();
MSR CPSR_c, #(NO_INT | SYS32_MODE) ; Change to SYS mode
BL OSIntExit ; OSIntExit();
; RESTORE TASK''S CONTEXT and RETURN TO TASK
LDR R4, [SP], #4 ; pop new task''s CPSR
MSR CPSR_cxsf, R4
LDR R0, [SP], #4 ; pop new task''s context
LDR R1, [SP], #4
LDR R2, [SP], #4
LDR R3, [SP], #4
LDR R4, [SP], #4
LDR R5, [SP], #4
LDR R6, [SP], #4
LDR R7, [SP], #4
LDR R8, [SP], #4
LDR R9, [SP], #4
LDR R10, [SP], #4
LDR R11, [SP], #4
LDR R12, [SP], #4
LDR LR, [SP], #4
LDR PC, [SP], #4
;======================================================
;*********************************************************************************************************
; FIQ Interrupt Service Routine
;*********************************************************************************************************
;??? RSEG CODE:CODE:NOROOT(2)
CODE32
OS_CPU_FIQ_ISR
STMFD SP!,{R1-R3} ; PUSH WORKING REGISTERS ONTO IRQ STACK
MOV R1,SP ; Save IRQ stack pointer
ADD SP,SP,#12 ; Adjust FIQ stack pointer
SUB R2,LR,#4 ; Adjust PC for return address to task
MRS R3,SPSR ; Copy SPSR (i.e. interrupted task''s CPSR) to R3
MSR CPSR_c,#(NO_INT | SYS32_MODE) ; Change to SYS mode
; SAVE TASK''S CONTEXT ONTO TASK''S STACK
STMFD SP!,{R2} ; Push task''s Return PC
STMFD SP!,{R4-R12,LR} ; Push task''s LR,R12-R4
LDMFD R1!,{R4-R6} ; Move task''s R1-R3 from IRQ stack to SYS stack
STMFD SP!,{R4-R6}
STMFD SP!,{R0} ; Push task''s R0 onto task''s stack
STMFD SP!,{R3} ; Push task''s CPSR (i.e. IRQ''s SPSR)
; HANDLE NESTING COUNTER
LDR R0,addr_OSIntNesting ; OSIntNesting++;
LDRB R1,[R0]
ADD R1,R1,#1
STRB R1,[R0]
CMP R1,#1 ; if (OSIntNesting == 1) {
BNE OS_CPU_FIQ_ISR_1
LDR R4,addr_OSTCBCur ; OSTCBCur->OSTCBStkPtr = SP
LDR R5,[R4]
STR SP,[R5] ; }
OS_CPU_FIQ_ISR_1
MSR CPSR_c,#(NO_INT | FIQ32_MODE) ; Change to FIQ mode (to use the FIQ stack to handle interrupt)
BL OS_CPU_FIQ_ISR_Handler ; OS_CPU_FIQ_ISR_Handler();
MSR CPSR_c,#(NO_INT | SYS32_MODE) ; Change to SYS mode
BL OSIntExit ; OSIntExit();
; RESTORE TASK''S CONTEXT and RETURN TO TASK
LDMFD SP!,{R4} ; pop new task''s CPSR
MSR CPSR_cxsf,r4
LDMFD SP!,{R0-R12,LR,PC} ; pop new task''s R0-R12,LR & PC
;*********************************************************************************************************
; POINTERS TO VARIABLES
;*********************************************************************************************************
; DATA
; AREA data,DATA
;??OS_IntNesting:
; DC32 OSIntNesting
addr_OSIntNesting
DCD OSIntNesting
;??OS_PrioCur:
; DC32 OSPrioCur
addr_OSPrioCur
DCD OSPrioCur
;??OS_PrioHighRdy:
; DC32 OSPrioHighRdy
addr_OSPrioHighRdy
DCD OSPrioHighRdy
;??OS_Running:
; DC32 OSRunning
addr_OSRunning
DCD OSRunning
;??OS_TCBCur:
; DC32 OSTCBCur
addr_OSTCBCur
DCD OSTCBCur
;??OS_TCBHighRdy:
; DC32 OSTCBHighRdy
addr_OSTCBHighRdy
DCD OSTCBHighRdy
END
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