www.pudn.com > AN-1256.zip > os_cpu_a.s
;********************************************************************************************************
; uC/OS-II
; The Real-Time Kernel
;
; ATmega256 Specific code
; ICC AVR Compiler
;
;
; File : OS_CPU_A.S
; By : Jean J. Labrosse
;********************************************************************************************************
.include "os_cpu_i.h"
;/*$PAGE*/.
;********************************************************************************************************
; DISABLE/ENABLE INTERRUPTS USING OS_CRITICAL_METHOD #3
;
; Description : These functions are used to disable and enable interrupts using OS_CRITICAL_METHOD #3.
;
; OS_CPU_SR OSCPUSaveSR (void)
; Get current value of SREG
; Disable interrupts
; Return original value of SREG
;
; void OSCPURestoreSR (OS_CPU_SR cpu_sr)
; Set SREG to cpu_sr
; Return
;********************************************************************************************************
.area text(rel)
_OS_CPU_SR_Save::
IN R16,SREG ; Get current state of interrupts disable flag
CLI ; Disable interrupts
RET ; Return original SREG value in R16
_OS_CPU_SR_Restore::
OUT SREG,R16 ; Restore SREG
RET ; Return
;/*$PAGE*/.
;********************************************************************************************************
; START HIGHEST PRIORITY TASK READY-TO-RUN
;
; Description : This function is called by OSStart() to start the highest priority task that was created
; by your application before calling OSStart().
;
; Note(s) : 1) The (data)stack frame is assumed to look as follows:
;
; 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
; PCH
; PCL (High memory)
;
; where the stack pointer points to the task start address.
;
;
; 2) OSStartHighRdy() MUST:
; a) Call OSTaskSwHook() then,
; b) Set OSRunning to TRUE,
; c) Switch to the highest priority task.
;********************************************************************************************************
_OSStartHighRdy::
CALL _OSTaskSwHook ; Invoke user defined context switch hook
LDS R16,_OSRunning ; Indicate that we are multitasking
INC R16 ;
STS _OSRunning,R16 ;
LDS R30,_OSTCBHighRdy ; Let Z point to TCB of highest priority task
LDS R31,_OSTCBHighRdy+1 ; ready to run
LD R28,Z+ ; Load Y (R29:R28) pointer
LD R29,Z+ ;
POP_SP ; Restore stack pointer
POP_SREG_INT ; Restore status register (Disable Interrupts)
POP_ALL ; Restore all registers
RETI ; Start task
;/*$PAGE*/.
;********************************************************************************************************
; TASK LEVEL CONTEXT SWITCH
;
; Description : This function is called when a task makes a higher priority task ready-to-run.
;
; Note(s) : 1) Upon entry,
; OSTCBCur points to the OS_TCB of the task to suspend
; OSTCBHighRdy points to the OS_TCB of the task to resume
;
; 2) The stack frame of the task to suspend looks as follows:
;
; SP+0 --> LSB of task code address
; +1 MSB of task code address (High memory)
;
; 3) The saved context of the task to resume looks as follows:
;
; OSTCBHighRdy->OSTCBStkPtr --> SPL of (return) stack pointer (Low memory)
; SPH of (return) stack pointer
; Flags to load in status register
; RAMPZ
; R31
; R30
; R27
; .
; .
; R0
; PCH
; PCL (High memory)
;********************************************************************************************************
_OSCtxSw::
PUSH_ALL ; Save current task's context
PUSH_SREG
PUSH_SP
LDS R30,_OSTCBCur ; Z = OSTCBCur->OSTCBStkPtr
LDS R31,_OSTCBCur+1 ;
ST Z+,R28 ; Save Y (R29:R28) pointer
ST Z+,R29 ;
CALL _OSTaskSwHook ; Call user defined task switch hook
LDS R16,_OSPrioHighRdy ; OSPrioCur = OSPrioHighRdy
STS _OSPrioCur,R16
LDS R30,_OSTCBHighRdy ; Let Z point to TCB of highest priority task
LDS R31,_OSTCBHighRdy+1 ; ready to run
STS _OSTCBCur,R30 ; OSTCBCur = OSTCBHighRdy
STS _OSTCBCur+1,R31 ;
LD R28,Z+ ; Restore Y pointer
LD R29,Z+ ;
POP_SP ; Restore stack pointer
LD R16,Y+ ; Restore status register
SBRC R16,7 ; Skip next instruction if interrupts DISABLED
RJMP _OSCtxSw_1
OUT SREG,R16 ; Interrupts of task to return to are DISABLED
POP_ALL
RET
_OSCtxSw_1: CBR R16,BIT07 ; Interrupts of task to return to are ENABLED
OUT SREG,R16
POP_ALL ; Restore all registers
RETI
;/*$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:
;
; 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
; PCH
; PCL (High memory)
;
; 3) The saved context of the task to resume looks as follows:
;
; 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
; PCH
; PCL (High memory)
;*********************************************************************************************************
_OSIntCtxSw::
CALL _OSTaskSwHook ; Call user defined task switch hook
LDS R16,_OSPrioHighRdy ; OSPrioCur = OSPrioHighRdy
STS _OSPrioCur,R16 ;
LDS R30,_OSTCBHighRdy ; Z = OSTCBHighRdy->OSTCBStkPtr
LDS R31,_OSTCBHighRdy+1 ;
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 if 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