📄 os_cpu_a.lst
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ARM Macro Assembler Page 1
1 00000000 ;*******************************************************
*************************************************
2 00000000 ; uC/OS-II
3 00000000 ; The Real-Time
Kernel
4 00000000 ;
5 00000000 ; (c) Copyright 1992-2006,
Micrium, Weston, FL
6 00000000 ; All Rights Re
served
7 00000000 ;
8 00000000 ; Generic ARM
Port
9 00000000 ;
10 00000000 ; File : OS_CPU_A.ASM
11 00000000 ; Version : V2.86
12 00000000 ; By : Jean J. Labrosse
13 00000000 ;
14 00000000 ; For : ARMv7M Cortex-M3
15 00000000 ; Mode : Thumb2
16 00000000 ; Toolchain : RealView Development Suite
17 00000000 ; RealView Microcontroller Development Kit (
MDK)
18 00000000 ; ARM Developer Suite (ADS)
19 00000000 ; Keil uVision
20 00000000 ;*******************************************************
*************************************************
21 00000000
22 00000000 ;*******************************************************
*************************************************
23 00000000 ; PUBLIC FUNCT
IONS
24 00000000 ;*******************************************************
*************************************************
25 00000000
26 00000000 EXTERN OSRunning ; External referenc
es
27 00000000 EXTERN OSPrioCur
28 00000000 EXTERN OSPrioHighRdy
29 00000000 EXTERN OSTCBCur
30 00000000 EXTERN OSTCBHighRdy
31 00000000 EXTERN OSIntNesting
32 00000000 EXTERN OSIntExit
33 00000000 EXTERN OSTaskSwHook
34 00000000
35 00000000
36 00000000 EXPORT OS_CPU_SR_Save ; Functions decl
ared in this file
37 00000000 EXPORT OS_CPU_SR_Restore
38 00000000 EXPORT OSStartHighRdy
39 00000000 EXPORT OSCtxSw
40 00000000 EXPORT OSIntCtxSw
41 00000000 EXPORT PendSV_Handler
42 00000000
43 00000000 ;*******************************************************
*************************************************
44 00000000 ; EQUATES
ARM Macro Assembler Page 2
45 00000000 ;*******************************************************
*************************************************
46 00000000
47 00000000 E000ED04
NVIC_INT_CTRL
EQU 0xE000ED04 ; Interrupt control
state register.
48 00000000 E000ED22
NVIC_SYSPRI14
EQU 0xE000ED22 ; System priority r
egister (priority 1
4).
49 00000000 000000FF
NVIC_PENDSV_PRI
EQU 0xFF ; PendSV priority v
alue (lowest).
50 00000000 10000000
NVIC_PENDSVSET
EQU 0x10000000 ; Value to trigger
PendSV exception.
51 00000000
52 00000000 ;*******************************************************
*************************************************
53 00000000 ; CODE GENERATION D
IRECTIVES
54 00000000 ;*******************************************************
*************************************************
55 00000000
56 00000000 AREA |.text|, CODE, READONLY, ALIGN=
2
57 00000000 THUMB
58 00000000 REQUIRE8
59 00000000 PRESERVE8
60 00000000
61 00000000 ;*******************************************************
*************************************************
62 00000000 ; CRITICAL SECTION MET
HOD 3 FUNCTIONS
63 00000000 ;
64 00000000 ; Description: Disable/Enable interrupts by preserving t
he state of interrupts. Generally speaking you
65 00000000 ; would store the state of the interrupt di
sable flag in the local variable 'cpu_sr' and then
66 00000000 ; disable interrupts. 'cpu_sr' is allocate
d in all of uC/OS-II's functions that need to
67 00000000 ; disable interrupts. You would restore th
e interrupt disable state by copying back 'cpu_sr'
68 00000000 ; into the CPU's status register.
69 00000000 ;
70 00000000 ; Prototypes : OS_CPU_SR OS_CPU_SR_Save(void);
71 00000000 ; void OS_CPU_SR_Restore(OS_CPU_S
R cpu_sr);
72 00000000 ;
73 00000000 ;
74 00000000 ; Note(s) : 1) These functions are used in general li
ke this:
75 00000000 ;
76 00000000 ; void Task (void *p_arg)
77 00000000 ; {
ARM Macro Assembler Page 3
78 00000000 ; #if OS_CRITICAL_METHOD == 3 /
* Allocate storage for CPU status register */
79 00000000 ; OS_CPU_SR cpu_sr;
80 00000000 ; #endif
81 00000000 ;
82 00000000 ; :
83 00000000 ; :
84 00000000 ; OS_ENTER_CRITICAL(); /
* cpu_sr = OS_CPU_SaveSR(); */
85 00000000 ; :
86 00000000 ; :
87 00000000 ; OS_EXIT_CRITICAL(); /
* OS_CPU_RestoreSR(cpu_sr); */
88 00000000 ; :
89 00000000 ; :
90 00000000 ; }
91 00000000 ;*******************************************************
*************************************************
92 00000000
93 00000000 OS_CPU_SR_Save
94 00000000 F3EF 8010 MRS R0, PRIMASK ; Set prio int mask
to mask all (excep
t faults)
95 00000004 B672 CPSID I
96 00000006 4770 BX LR
97 00000008
98 00000008 OS_CPU_SR_Restore
99 00000008 F380 8810 MSR PRIMASK, R0
100 0000000C 4770 BX LR
101 0000000E
102 0000000E ;*******************************************************
*************************************************
103 0000000E ; START MULTITA
SKING
104 0000000E ; void OSStartHigh
Rdy(void)
105 0000000E ;
106 0000000E ; Note(s) : 1) This function triggers a PendSV exception
(essentially, causes a context switch) to cause
107 0000000E ; the first task to start.
108 0000000E ;
109 0000000E ; 2) OSStartHighRdy() MUST:
110 0000000E ; a) Setup PendSV exception priority to low
est;
111 0000000E ; b) Set initial PSP to 0, to tell context
switcher this is first run;
112 0000000E ; c) Set OSRunning to TRUE;
113 0000000E ; d) Trigger PendSV exception;
114 0000000E ; e) Enable interrupts (tasks will run with
interrupts enabled).
115 0000000E ;*******************************************************
*************************************************
116 0000000E
117 0000000E OSStartHighRdy
118 0000000E 481D LDR R0, =NVIC_SYSPRI14 ; Set the Pe
ndSV exception prio
rity
119 00000010 F04F 01FF LDR R1, =NVIC_PENDSV_PRI
120 00000014 7001 STRB R1, [R0]
ARM Macro Assembler Page 4
121 00000016
122 00000016 2000 MOVS R0, #0 ; Set the PSP to 0
for initial context
switch call
123 00000018 F380 8809 MSR PSP, R0
124 0000001C
125 0000001C 481A LDR R0, =OSRunning
; OSRunning = TRUE
126 0000001E 2101 MOVS R1, #1
127 00000020 7001 STRB R1, [R0]
128 00000022
129 00000022 481A LDR R0, =NVIC_INT_CTRL ; Trigger th
e PendSV exception
(causes context swi
tch)
130 00000024 F04F 5180 LDR R1, =NVIC_PENDSVSET
131 00000028 6001 STR R1, [R0]
132 0000002A
133 0000002A B662 CPSIE I ; Enable interrupts
at processor level
134 0000002C
135 0000002C OSStartHang
136 0000002C E7FE B OSStartHang ; Should never get
here
137 0000002E
138 0000002E
139 0000002E ;*******************************************************
*************************************************
140 0000002E ; PERFORM A CONTEXT SWITCH
(From task level)
141 0000002E ; void OSCtxSw
(void)
142 0000002E ;
143 0000002E ; Note(s) : 1) OSCtxSw() is called when OS wants to perf
orm a task context switch. This function
144 0000002E ; triggers the PendSV exception which is wh
ere the real work is done.
145 0000002E ;*******************************************************
*************************************************
146 0000002E
147 0000002E OSCtxSw
148 0000002E 4817 LDR R0, =NVIC_INT_CTRL ; Trigger th
e PendSV exception
(causes context swi
tch)
149 00000030 F04F 5180 LDR R1, =NVIC_PENDSVSET
150 00000034 6001 STR R1, [R0]
151 00000036 4770 BX LR
152 00000038
153 00000038 ;*******************************************************
*************************************************
154 00000038 ; PERFORM A CONTEXT SWITCH (
From interrupt level)
155 00000038 ; void OSIntCtxS
w(void)
156 00000038 ;
157 00000038 ; Notes: 1) OSIntCtxSw() is called by OSIntExit() whe
n it determines a context switch is needed as
ARM Macro Assembler Page 5
158 00000038 ; the result of an interrupt. This functio
n simply triggers a PendSV exception which will
159 00000038 ; be handled when there are no more interru
pts active and interrupts are enabled.
160 00000038 ;*******************************************************
*************************************************
161 00000038
162 00000038 OSIntCtxSw
163 00000038 4814 LDR R0, =NVIC_INT_CTRL ; Trigger th
e PendSV exception
(causes context swi
tch)
164 0000003A F04F 5180 LDR R1, =NVIC_PENDSVSET
165 0000003E 6001 STR R1, [R0]
166 00000040 4770 BX LR
167 00000042
168 00000042 ;*******************************************************
*************************************************
169 00000042 ; HANDLE PendSV
EXCEPTION
170 00000042 ; void OS_CPU_PendSV
Handler(void)
171 00000042 ;
172 00000042 ; Note(s) : 1) PendSV is used to cause a context switch.
This is a recommended method for performing
173 00000042 ; context switches with Cortex-M3. This is
because the Cortex-M3 auto-saves half of the
174 00000042 ; processor context on any exception, and r
estores same on return from exception. So only
175 00000042 ; saving of R4-R11 is required and fixing u
p the stack pointers. Using the PendSV exception
176 00000042 ; this way means that context saving and re
storing is identical whether it is initiated from
177 00000042 ; a thread or occurs due to an interrupt or
exception.
178 00000042 ;
179 00000042 ; 2) Pseudo-code is:
180 00000042 ; a) Get the process SP, if 0 then skip (go
to d) the saving part (first context switch);
181 00000042 ; b) Save remaining regs r4-r11 on process
stack;
182 00000042 ; c) Save the process SP in its TCB, OSTCBC
ur->OSTCBStkPtr = SP;
183 00000042 ; d) Call OSTaskSwHook();
184 00000042 ; e) Get current high priority, OSPrioCur =
OSPrioHighRdy;
185 00000042 ; f) Get current ready thread TCB, OSTCBCur
= OSTCBHighRdy;
186 00000042 ; g) Get new process SP from TCB, SP = OSTC
BHighRdy->OSTCBStkPtr;
187 00000042 ; h) Restore R4-R11 from new process stack;
188 00000042 ; i) Perform exception return which will re
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