?? os_cpu_a.s90
字號:
;********************************************************************************************************
; uC/OS-II
; The Real-Time Kernel
;
; ATMEL AVR Specific code
;
;
; File : OS_CPU_A.S90
; By : Jean J. Labrosse
;********************************************************************************************************
#include "os_cpu_i.s90"
;********************************************************************************************************
; PUBLIC DECLARATIONS
;********************************************************************************************************
MODULE OS_CPU_A
PUBLIC OS_CPU_SR_Save
PUBLIC OS_CPU_SR_Restore
PUBLIC OSCtxSw
PUBLIC OSIntCtxSw
;********************************************************************************************************
; EXTERNAL DECLARATIONS
;********************************************************************************************************
EXTERN OSTCBCur
EXTERN OSTCBHighRdy
;/*$PAGE*/
;********************************************************************************************************
; DISABLE/ENABLE INTERRUPTS USING OS_CRITICAL_METHOD #3
;
; Description : These functions are used to disable and enable interrupts using OS_CRITICAL_METHOD #3.
;
; OS_CPU_SR OSCPUSaveSR (void)
; Get current value of SREG
; Disable interrupts
; Return original value of SREG
;
; void OSCPURestoreSR (OS_CPU_SR cpu_sr)
; Set SREG to cpu_sr
; Return
;********************************************************************************************************
RSEG CODE:CODE:NOROOT(1)
OS_CPU_SR_Save: IN R16,SREG ; Get current state of interrupts disable flag
CLI ; Disable interrupts
RET ; Return original SREG value in R16
OS_CPU_SR_Restore: OUT SREG,R16 ; Restore SREG
RET ; Return
;/*$PAGE*/
;********************************************************************************************************
; TASK LEVEL CONTEXT SWITCH
;
; Description : This function is called when a task makes a higher priority task ready-to-run.
;
; Note(s) : 1) Upon entry,
; OSTCBCur points to the OS_TCB of the task to suspend
; OSTCBHighRdy points to the OS_TCB of the task to resume
;
; 2) The stack frame of the task to suspend looks as follows:
;
; SP+0 --> LSB of task code address
; +1 MSB of task code address (High memory)
;
; 3) The saved context of the task to resume looks as follows:
;
; Hardware Stack points to EMPTY
; <----------------------------\
; PC (H) |
; PC (L) |
; |
; |
; OSTCBHighRdy->OSTCBStkPtr --> SPL of (return) stack pointer ----/ (Low memory)
; SPH of (return) stack pointer
; Flags to load in status register
; RAMPZ
; R31
; R30
; R27
; .
; .
; R0 (High memory)
;********************************************************************************************************
OSCtxSw: PUSH_ALL ; Save current task's context
PUSH_SREG
PUSH_SP
LDS R30,OSTCBCur ; Z = OSTCBCur->OSTCBStkPtr
LDS R31,OSTCBCur+1 ;
ST Z+,R28 ; Save Y (R29:R28) pointer
ST Z+,R29 ;
LDS R30,OSTCBHighRdy ; Let Z point to TCB of highest priority task
LDS R31,OSTCBHighRdy+1 ; ready to run
STS OSTCBCur,R30 ; OSTCBCur = OSTCBHighRdy
STS OSTCBCur+1,R31 ;
LD R28,Z+ ; Restore Y pointer
LD R29,Z+ ;
POP_SP ; Restore stack pointer
LD R16,Y+ ; Restore status register
SBRC R16,7 ; Skip next instruction in interrupts DISABLED
RJMP OSCtxSw_1
OUT SREG,R16 ; Interrupts of task to return to are DISABLED
POP_ALL
RET
OSCtxSw_1: CBR R16,BIT07 ; Interrupts of task to return to are ENABLED
OUT SREG,R16
POP_ALL ; Restore all registers
RETI
;/*$PAGE*/
;*********************************************************************************************************
; INTERRUPT LEVEL CONTEXT SWITCH
;
; Description : This function is called by OSIntExit() to perform a context switch to a task that has
; been made ready-to-run by an ISR.
;
; Note(s) : 1) Upon entry,
; OSTCBCur points to the OS_TCB of the task to suspend
; OSTCBHighRdy points to the OS_TCB of the task to resume
;
; 2) The stack frame of the task to suspend looks as follows:
;
; Hardware Stack points to EMPTY
; <----------------------------\
; PC (H) |
; PC (L) |
; |
; |
; OSTCBCur->OSTCBStkPtr ------> SPL of (return) stack pointer ---/ (Low memory)
; SPH of (return) stack pointer
; Flags to load in status register
; RAMPZ
; R31
; R30
; R27
; .
; .
; R0 (High memory)
;
; 3) The saved context of the task to resume looks as follows:
;
; Hardware Stack points to EMPTY
; <----------------------------\
; PC (H) |
; PC (L) |
; |
; |
; OSTCBHighRdy->OSTCBStkPtr --> SPL of (return) stack pointer ---/ (Low memory)
; SPH of (return) stack pointer
; Flags to load in status register
; RAMPZ
; R31
; R30
; R27
; .
; .
; R0 (High memory)
;*********************************************************************************************************
OSIntCtxSw:
LDS R30,OSTCBHighRdy ; Let Z point to TCB of highest priority task
LDS R31,OSTCBHighRdy+1 ; ready to run
STS OSTCBCur,R30 ; OSTCBCur = OSTCBHighRdy
STS OSTCBCur+1,R31 ;
LD R28,Z+ ; Restore Y pointer
LD R29,Z+ ;
POP_SP ; Restore stack pointer
LD R16,Y+ ; Restore status register
SBRC R16,7 ; Skip next instruction in interrupts DISABLED
RJMP OSIntCtxSw_1
OUT SREG,R16 ; Interrupts of task to return to are DISABLED
POP_ALL
RET
OSIntCtxSw_1: CBR R16,BIT07 ; Interrupts of task to return to are ENABLED
OUT SREG,R16
POP_ALL ; Restore all registers
RETI
END
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