?? os_cpu_a.asm
字號:
;********************************************************************************************************
; uC/OS-II
; The Real-Time Kernel
; 全面版
;
; (c) Copyright 1992-2002, Jean J. Labrosse, Weston, FL
; All Rights Reserved
;
;
; 80x86/80x88 Specific code
; LARGE MEMORY MODEL WITH FLOATING-POINT
; Borland C/C++ V4.51
;
; File : OS_CPU_A.ASM
; By : Jean J. Labrosse
;********************************************************************************************************
PUBLIC _OSStartHighRdy
PUBLIC _OSCtxSw
PUBLIC _OSIntCtxSw
PUBLIC _OSFPRestore
PUBLIC _OSFPSave
PUBLIC _OSTickISR
EXTRN _OSIntExit:FAR
EXTRN _OSTimeTick:FAR
EXTRN _OSTaskSwHook:FAR
EXTRN _OSIntNesting:BYTE
EXTRN _OSTickDOSCtr:BYTE
EXTRN _OSPrioHighRdy:BYTE
EXTRN _OSPrioCur:BYTE
EXTRN _OSRunning:BYTE
EXTRN _OSTCBCur:DWORD
EXTRN _OSTCBHighRdy:DWORD
.MODEL LARGE
.CODE
.186
PAGE ; /*$PAGE*/
;*********************************************************************************************************
; START MULTITASKING
; void OSStartHighRdy(void)
;
; The stack frame is assumed to look as follows:
;
; OSTCBHighRdy->OSTCBStkPtr --> DS (Low memory)
; ES
; DI
; SI
; BP
; SP
; BX
; DX
; CX
; AX
; OFFSET of task code address
; SEGMENT of task code address
; Flags to load in PSW
; OFFSET of task code address
; SEGMENT of task code address
; OFFSET of 'pdata'
; SEGMENT of 'pdata' (High memory)
;
; Note : OSStartHighRdy() MUST:
; a) Call OSTaskSwHook() then,
; b) Set OSRunning to TRUE,
; c) Switch to the highest priority task.
;*********************************************************************************************************
_OSStartHighRdy PROC FAR
CALL FAR PTR _OSTaskSwHook ; Call user defined task switch hook
;
MOV AX, SEG _OSTCBHighRdy ; Reload DS
MOV DS, AX ;
MOV AL, 1 ; OSRunning = TRUE;
MOV BYTE PTR DS:_OSRunning, AL ; (Indicates that multitasking has started)
;
LES BX, DWORD PTR DS:_OSTCBHighRdy ; SS:SP = OSTCBHighRdy->OSTCBStkPtr
MOV SS, ES:[BX+2] ;
MOV SP, ES:[BX+0] ;
;
POP DS ; Load task's context
POP ES ;
POPA ;
;
IRET ; Run task
_OSStartHighRdy ENDP
PAGE ; /*$PAGE*/
;*********************************************************************************************************
; PERFORM A CONTEXT SWITCH (From task level)
; void OSCtxSw(void)
; 從任務層中執行任務轉換
;
; 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 -> OFFSET of task to suspend (Low memory)
; SEGMENT of task to suspend
; PSW of task to suspend (High memory)
;
; 3) The stack frame of the task to resume looks as follows:
;
; OSTCBHighRdy->OSTCBStkPtr --> DS (Low memory)
; ES
; DI
; SI
; BP
; SP
; BX
; DX
; CX
; AX
; OFFSET of task code address
; SEGMENT of task code address
; Flags to load in PSW (High memory)
;*********************************************************************************************************
_OSCtxSw PROC FAR
;
PUSHA ; Save current task's context
;PUSHA、POPA指令將所有通用寄存器的內容壓入或者彈出堆棧。壓入的
;順序是：AX，CX，DX，BX，SP，BP，SI，DI（SP是執行該指令之前的值）彈出的順序與壓入相反
PUSH ES ; 接下來是ES
PUSH DS ; 接下來是DS（見第二版書389頁）
;
MOV AX, SEG _OSTCBCur ; Reload DS in case it was altered
MOV DS, AX ;
;如果DS改變的話，就重裝DS
LES BX, DWORD PTR DS:_OSTCBCur ; OSTCBCur->OSTCBStkPtr = SS:SP
MOV ES:[BX+2], SS ; OSTCBHighRdy->OSTCBStkPtr --> DS
MOV ES:[BX+0], SP ;
;
CALL FAR PTR _OSTaskSwHook ; Call user defined task switch hook
;
MOV AX, WORD PTR DS:_OSTCBHighRdy+2 ; OSTCBCur = OSTCBHighRdy
MOV DX, WORD PTR DS:_OSTCBHighRdy ; 因為是32位指令
MOV WORD PTR DS:_OSTCBCur+2, AX ; 將最高優先級TCB賦給OSTCBCur
MOV WORD PTR DS:_OSTCBCur, DX ;
;
MOV AL, BYTE PTR DS:_OSPrioHighRdy ; OSPrioCur = OSPrioHighRdy
MOV BYTE PTR DS:_OSPrioCur, AL ; 將最高優先級值賦給 OSPrioCur
;
LES BX, DWORD PTR DS:_OSTCBHighRdy ; SS:SP = OSTCBHighRdy->OSTCBStkPtr
MOV SS, ES:[BX+2] ;LES是地址傳送指令，將源地址傳送到ES寄存器
MOV SP, ES:[BX] ;
;
POP DS ; Load new task's context
POP ES ; 出棧
POPA ;
;
IRET ; Return to new task中斷返回指令
;
_OSCtxSw ENDP
PAGE ; /*$PAGE*/
;*********************************************************************************************************
; PERFORM A CONTEXT SWITCH (From an ISR)
; void OSIntCtxSw(void)
; 從中斷層中執行任務轉換
;
; Note(s): 1) Upon entry,
; OSTCBCur points to the OS_TCB of the task to suspend
; OSTCBCur 指向要掛起任務的OS_TCB
; OSTCBHighRdy 指向要恢復任務的OS_TCB
;
; 2) The stack frame of the task to suspend looks as follows:
;要掛起任務的堆棧結構如下：
; OSTCBCur->OSTCBStkPtr ------> DS (Low memory)
; ES
; DI
; SI
; BP
; SP
; BX
; DX
; CX
; AX
; OFFSET of task code address
; SEGMENT of task code address
; Flags to load in PSW (High memory)
;
; 3) The stack frame of the task to resume looks as follows:
;要恢復任務的堆棧結構如下：
; OSTCBHighRdy->OSTCBStkPtr --> DS (Low memory)
; ES
; DI
; SI
; BP
; SP
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