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CortexM3/OS_Target_asm.s@7:6fab7e5aa489, 2010-11-11 (annotated)

Committer:: segundo
Date:: Thu Nov 11 10:30:39 2010 +0000
Revision:: 7:6fab7e5aa489
Parent:: 0:d7810ff946c1

Who changed what in which revision?

User	Revision	Line number	New contents of line
segundo	0:d7810ff946c1	1	; ******************************************************************************
segundo	0:d7810ff946c1	2	; *
segundo	0:d7810ff946c1	3	; * FULLNAME: Single-Chip Microcontroller Real-Time Operating System
segundo	0:d7810ff946c1	4	; *
segundo	0:d7810ff946c1	5	; * NICKNAME: scmRTOS
segundo	0:d7810ff946c1	6	; *
segundo	0:d7810ff946c1	7	; * PROCESSOR: ARM Cortex-M3
segundo	0:d7810ff946c1	8	; *
segundo	0:d7810ff946c1	9	; * TOOLKIT: EWARM (IAR Systems)
segundo	0:d7810ff946c1	10	; *
segundo	0:d7810ff946c1	11	; * PURPOSE: Target Dependent Low-Level Stuff
segundo	0:d7810ff946c1	12	; *
segundo	0:d7810ff946c1	13	; * Version: 3.10
segundo	0:d7810ff946c1	14	; *
segundo	0:d7810ff946c1	15	; * $Revision: 195 $
segundo	0:d7810ff946c1	16	; * $Date:: 2008-06-19 #$
segundo	0:d7810ff946c1	17	; *
segundo	0:d7810ff946c1	18	; * Copyright (c) 2003-2010, Harry E. Zhurov
segundo	0:d7810ff946c1	19	; *
segundo	0:d7810ff946c1	20	; * Permission is hereby granted, free of charge, to any person
segundo	0:d7810ff946c1	21	; * obtaining a copy of this software and associated documentation
segundo	0:d7810ff946c1	22	; * files (the "Software"), to deal in the Software without restriction,
segundo	0:d7810ff946c1	23	; * including without limitation the rights to use, copy, modify, merge,
segundo	0:d7810ff946c1	24	; * publish, distribute, sublicense, and/or sell copies of the Software,
segundo	0:d7810ff946c1	25	; * and to permit persons to whom the Software is furnished to do so,
segundo	0:d7810ff946c1	26	; * subject to the following conditions:
segundo	0:d7810ff946c1	27	; *
segundo	0:d7810ff946c1	28	; * The above copyright notice and this permission notice shall be included
segundo	0:d7810ff946c1	29	; * in all copies or substantial portions of the Software.
segundo	0:d7810ff946c1	30	; *
segundo	0:d7810ff946c1	31	; * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
segundo	0:d7810ff946c1	32	; * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
segundo	0:d7810ff946c1	33	; * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
segundo	0:d7810ff946c1	34	; * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
segundo	0:d7810ff946c1	35	; * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
segundo	0:d7810ff946c1	36	; * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH
segundo	0:d7810ff946c1	37	; * THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
segundo	0:d7810ff946c1	38	; *
segundo	0:d7810ff946c1	39	; * =================================================================
segundo	0:d7810ff946c1	40	; * See http://scmrtos.sourceforge.net for documentation, latest
segundo	0:d7810ff946c1	41	; * information, license and contact details.
segundo	0:d7810ff946c1	42	; * =================================================================
segundo	0:d7810ff946c1	43	; *
segundo	0:d7810ff946c1	44	; ******************************************************************************
segundo	0:d7810ff946c1	45	; * Ported by Andrey Chuikin, Copyright (c) 2008-2010
segundo	0:d7810ff946c1	46
segundo	0:d7810ff946c1	47	; #include "scmRTOS_TARGET_CFG.h"
segundo	0:d7810ff946c1	48
segundo	0:d7810ff946c1	49	; -----------------------------------------------------------------------------
segundo	0:d7810ff946c1	50	; PUBLIC FUNCTIONS
segundo	0:d7810ff946c1	51	;
segundo	0:d7810ff946c1	52	EXTERN OS_ContextSwitchHook
segundo	0:d7810ff946c1	53
segundo	0:d7810ff946c1	54	EXPORT OS_Start
segundo	0:d7810ff946c1	55	EXPORT PendSV_Handler
segundo	0:d7810ff946c1	56
segundo	0:d7810ff946c1	57	; -----------------------------------------------------------------------------
segundo	0:d7810ff946c1	58	; EQUATES
segundo	0:d7810ff946c1	59	;
segundo	0:d7810ff946c1	60	NVIC_INT_CTRL EQU 0xE000ED04 ; Interrupt control state register.
segundo	0:d7810ff946c1	61	NVIC_PENDSVSET EQU 0x10000000 ; Value to trigger PendSV exception.
segundo	0:d7810ff946c1	62
segundo	0:d7810ff946c1	63	NVIC_SYSPRI14 EQU 0xE000ED22 ; System priority register (priority 14).
segundo	0:d7810ff946c1	64	NVIC_PENDSV_PRI EQU 0xFF ; PendSV priority value (lowest).
segundo	0:d7810ff946c1	65	NVIC_SYSPRI15 EQU 0xE000ED23 ; System priority register (priority 15).
segundo	0:d7810ff946c1	66	NVIC_ST_PRI EQU 0xFF ; SysTick priority value (lowest).
segundo	0:d7810ff946c1	67
segundo	0:d7810ff946c1	68	NVIC_ST_CTRL EQU 0xE000E010 ; SysTick Ctrl & Status Reg.
segundo	0:d7810ff946c1	69	NVIC_ST_RELOAD EQU 0xE000E014 ; SysTick Reload Value Reg.
segundo	0:d7810ff946c1	70	NVIC_ST_CTRL_CLK_SRC EQU 0x00000004 ; Clock Source.
segundo	0:d7810ff946c1	71	NVIC_ST_CTRL_INTEN EQU 0x00000002 ; Interrupt enable.
segundo	0:d7810ff946c1	72	NVIC_ST_CTRL_ENABLE EQU 0x00000001 ; Counter mode.
segundo	0:d7810ff946c1	73
segundo	0:d7810ff946c1	74	; should be the same as in scmRTOS_TARGET_CFG.h
segundo	0:d7810ff946c1	75	SYSTICKFREQ EQU 100000000
segundo	0:d7810ff946c1	76	SYSTICKINTRATE EQU 1000
segundo	0:d7810ff946c1	77
segundo	0:d7810ff946c1	78	; -----------------------------------------------------------------------------
segundo	0:d7810ff946c1	79	; CODE GENERATION DIRECTIVES
segundo	0:d7810ff946c1	80	;
segundo	0:d7810ff946c1	81	AREA TEXT, CODE, READONLY
segundo	0:d7810ff946c1	82	THUMB
segundo	0:d7810ff946c1	83
segundo	0:d7810ff946c1	84	; -----------------------------------------------------------------------------
segundo	0:d7810ff946c1	85	; HANDLE PendSV EXCEPTION
segundo	0:d7810ff946c1	86	; void PendSV_Handler(void)
segundo	0:d7810ff946c1	87	;
segundo	0:d7810ff946c1	88	; Note(s) : 1) PendSV is used to cause a context switch. This is a recommended method for performing
segundo	0:d7810ff946c1	89	; context switches with Cortex-M3. This is because the Cortex-M3 auto-saves half of the
segundo	0:d7810ff946c1	90	; processor context on any exception, and restores same on return from exception. So only
segundo	0:d7810ff946c1	91	; saving of R4-R11 is required and fixing up the stack pointers. Using the PendSV exception
segundo	0:d7810ff946c1	92	; this way means that context saving and restoring is identical whether it is initiated from
segundo	0:d7810ff946c1	93	; a thread or occurs due to an interrupt or exception.
segundo	0:d7810ff946c1	94	;
segundo	0:d7810ff946c1	95	; 2) Pseudo-code is:
segundo	0:d7810ff946c1	96	; a) Get the process SP, if 0 then skip (goto f) the saving part (first context switch);
segundo	0:d7810ff946c1	97	; b) Save remaining regs r4-r11 on process stack;
segundo	0:d7810ff946c1	98	; c) Call OS_ContextSwitchHook for save current task SP and get new task SP;
segundo	0:d7810ff946c1	99	; d) Restore R4-R11 from new process stack;
segundo	0:d7810ff946c1	100	; e) Perform exception return which will restore remaining context.
segundo	0:d7810ff946c1	101	; f) Get SP for the first context switch (R2 hold it);
segundo	0:d7810ff946c1	102	; run SysTick; goto d);
segundo	0:d7810ff946c1	103	;
segundo	0:d7810ff946c1	104	; 3) On entry into PendSV handler:
segundo	0:d7810ff946c1	105	; a) The following have been saved on the process stack (by processor):
segundo	0:d7810ff946c1	106	; xPSR, PC, LR, R12, R0-R3
segundo	0:d7810ff946c1	107	; b) Processor mode is switched to Handler mode (from Thread mode)
segundo	0:d7810ff946c1	108	; c) Stack is Main stack (switched from Process stack)
segundo	0:d7810ff946c1	109	;
segundo	0:d7810ff946c1	110	; 4) Since PendSV is set to lowest priority in the system (by OS_Start() below), we
segundo	0:d7810ff946c1	111	; know that it will only be run when no other exception or interrupt is active, and
segundo	0:d7810ff946c1	112	; therefore safe to assume that context being switched out was using the process stack (PSP).
segundo	0:d7810ff946c1	113	;
segundo	0:d7810ff946c1	114	PendSV_Handler
segundo	0:d7810ff946c1	115	CPSID I ; Prevent interruption during context switch
segundo	0:d7810ff946c1	116	MRS R0, PSP ; PSP is process stack pointer
segundo	0:d7810ff946c1	117	CBZ R0, nosave ; Skip register save the first time
segundo	0:d7810ff946c1	118
segundo	0:d7810ff946c1	119	STMDB R0!, {R4-R11} ; Save remaining regs r4-11 on process stack
segundo	0:d7810ff946c1	120	; At this point, entire context of process has been saved
segundo	0:d7810ff946c1	121
segundo	0:d7810ff946c1	122	PUSH {R14} ; Save LR exc_return value
segundo	0:d7810ff946c1	123	LDR R1, =OS_ContextSwitchHook ; OS_ContextSwitchHook();
segundo	0:d7810ff946c1	124	BLX R1
segundo	0:d7810ff946c1	125	POP {R14}
segundo	0:d7810ff946c1	126
segundo	0:d7810ff946c1	127	ContextRestore
segundo	0:d7810ff946c1	128	; R0 is new process SP;
segundo	0:d7810ff946c1	129	LDMIA R0!, {R4-R11} ; Restore r4-11 from new process stack
segundo	0:d7810ff946c1	130	MSR PSP, R0 ; Load PSP with new process SP
segundo	0:d7810ff946c1	131	ORR LR, LR, #0x04 ; Ensure exception return uses process stack
segundo	0:d7810ff946c1	132	CPSIE I
segundo	0:d7810ff946c1	133	BX LR ; Exception return will restore remaining context
segundo	0:d7810ff946c1	134	nosave
segundo	0:d7810ff946c1	135	MOV R0, R2 ; R2 hold the first task SP
segundo	0:d7810ff946c1	136
segundo	0:d7810ff946c1	137	LDR R1, =NVIC_ST_CTRL ; Enable and run SysTick
segundo	0:d7810ff946c1	138	LDR R2, =(NVIC_ST_CTRL_CLK_SRC :OR: NVIC_ST_CTRL_INTEN :OR: NVIC_ST_CTRL_ENABLE)
segundo	0:d7810ff946c1	139	STR R2, [R1]
segundo	0:d7810ff946c1	140
segundo	0:d7810ff946c1	141	B ContextRestore
segundo	0:d7810ff946c1	142
segundo	0:d7810ff946c1	143
segundo	0:d7810ff946c1	144	; -----------------------------------------------------------------------------
segundo	0:d7810ff946c1	145	; START MULTITASKING
segundo	0:d7810ff946c1	146	; void OS_Start(TStackItem* sp)
segundo	0:d7810ff946c1	147	;
segundo	0:d7810ff946c1	148	; Note(s) : 1) OS_Start() MUST:
segundo	0:d7810ff946c1	149	; a) Setup PendSV and SysTick exception priority to lowest;
segundo	0:d7810ff946c1	150	; b) Setup SysTick (reload value);
segundo	0:d7810ff946c1	151	; c) Enable interrupts (tasks will run with interrupts enabled).
segundo	0:d7810ff946c1	152	;
segundo	0:d7810ff946c1	153	OS_Start
segundo	0:d7810ff946c1	154	LDR R1, =NVIC_SYSPRI14 ; Set the PendSV exception priority (lowest)
segundo	0:d7810ff946c1	155	LDR R2, =NVIC_PENDSV_PRI
segundo	0:d7810ff946c1	156	STRB R2, [R1]
segundo	0:d7810ff946c1	157	LDR R1, =NVIC_SYSPRI15 ; Set the SysTick exception priority (lowest)
segundo	0:d7810ff946c1	158	LDR R2, =NVIC_ST_PRI
segundo	0:d7810ff946c1	159	STRB R2, [R1]
segundo	0:d7810ff946c1	160
segundo	0:d7810ff946c1	161	LDR R1, =NVIC_ST_RELOAD ; Setup SysTick
segundo	0:d7810ff946c1	162	LDR R2, =(SYSTICKFREQ/SYSTICKINTRATE-1)
segundo	0:d7810ff946c1	163	STR R2, [R1]
segundo	0:d7810ff946c1	164
segundo	0:d7810ff946c1	165	MOV R2, R0 ; Save the first task stack
segundo	0:d7810ff946c1	166	MOVS R0, #0 ; Set the PSP to 0 for initial context switch call
segundo	0:d7810ff946c1	167	MSR PSP, R0
segundo	0:d7810ff946c1	168
segundo	0:d7810ff946c1	169	LDR R0, =NVIC_INT_CTRL ; Trigger the PendSV exception (causes context switch)
segundo	0:d7810ff946c1	170	LDR R1, =NVIC_PENDSVSET
segundo	0:d7810ff946c1	171	STR R1, [R0]
segundo	0:d7810ff946c1	172
segundo	0:d7810ff946c1	173	CPSIE I ; Enable interrupts at processor level
segundo	0:d7810ff946c1	174	loop
segundo	0:d7810ff946c1	175	B loop ; Should never get here
segundo	0:d7810ff946c1	176
segundo	0:d7810ff946c1	177
segundo	0:d7810ff946c1	178	END

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Type:	Library
Created:	11 Nov 2010
Imports:	8
Forks:	0
Commits:	8
Dependents:	0
Dependencies:	0
Followers:	1

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CortexM3/OS_Target_asm.s@7:6fab7e5aa489, 2010-11-11 (annotated)

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