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Posted on:
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hello,
Firstly , i am a new to G++....so pls help me from that point of
view.....i have a C++ code written and i am using RTC interrupt.....sm
part of the code troubles if system has an interrupt.....the code
particularly troubles when accessing "some" Global Objects.....here is
how my startup file looks....i have just picked it up from one of the
examples in winarm....Please suggest if any changes have to be done
either to the startup file or any other change......My ISR only sets a
flag (unsigned char variable to TRUE)and so no "heavy code " goes in
ISR...
my start up file......
.global main // int main(void)
.global _etext // -> .data initial values in
ROM
.global _data // -> .data area in RAM
.global _edata // end of .data area
.global __bss_start // -> .bss area in RAM
.global _bss_end_ // end of .bss area
.global _stack // top of stack
// Stack Sizes
.set UND_STACK_SIZE, 0x00000004
.set ABT_STACK_SIZE, 0x00000004
.set FIQ_STACK_SIZE, 0x00000004
.set IRQ_STACK_SIZE, 0X00000080
.set SVC_STACK_SIZE, 0x00000004
// Standard definitions of Mode bits and Interrupt (I & F) flags in PSRs
.set MODE_USR, 0x10 // User Mode
.set MODE_FIQ, 0x11 // FIQ Mode
.set MODE_IRQ, 0x12 // IRQ Mode
.set MODE_SVC, 0x13 // Supervisor Mode
.set MODE_ABT, 0x17 // Abort Mode
.set MODE_UND, 0x1B // Undefined Mode
.set MODE_SYS, 0x1F // System Mode
.equ I_BIT, 0x80 // when I bit is set, IRQ is
disabled
.equ F_BIT, 0x40 // when F bit is set, FIQ is
disabled
.text
.code 32
.align 2
.global _boot
.func _boot
_boot:
// Runtime Interrupt Vectors
// -------------------------
Vectors:
b _start // reset - _start
ldr pc,_undf // undefined - _undf
ldr pc,_swi // SWI - _swi
ldr pc,_pabt // program abort - _pabt
ldr pc,_dabt // data abort - _dabt
nop // reserved
ldr pc,[pc,#-0xFF0] // IRQ - read the VIC
ldr pc,_fiq // FIQ - _fiq
#if 0
// Use this group for production
_undf: .word _reset // undefined - _reset
_swi: .word _reset // SWI - _reset
_pabt: .word _reset // program abort - _reset
_dabt: .word _reset // data abort - _reset
_irq: .word _reset // IRQ - _reset
_fiq: .word _reset // FIQ - _reset
#else
// Use this group for development
_undf: .word __undf // undefined
_swi: .word __swi // SWI
_pabt: .word __pabt // program abort
_dabt: .word __dabt // data abort
_irq: .word __irq // IRQ
_fiq: .word __fiq // FIQ
__undf: b . // undefined
__swi: b . // SWI
__pabt: b . // program abort
__dabt: b . // data abort
__irq: b . // IRQ
__fiq: b . // FIQ
#endif
.size _boot, . - _boot
.endfunc
// Setup the operating mode & stack.
// ---------------------------------
.global _start, start, _mainCRTStartup
.func _start
_start:
start:
_mainCRTStartup:
// Initialize Interrupt System
// - Set stack location for each mode
// - Leave in System Mode with Interrupts Disabled
// -----------------------------------------------
ldr r0,=_stack
msr CPSR_c,#MODE_UND|I_BIT|F_BIT // Undefined Instruction Mode
mov sp,r0
sub r0,r0,#UND_STACK_SIZE
msr CPSR_c,#MODE_ABT|I_BIT|F_BIT // Abort Mode
mov sp,r0
sub r0,r0,#ABT_STACK_SIZE
msr CPSR_c,#MODE_FIQ|I_BIT|F_BIT // FIQ Mode
mov sp,r0
sub r0,r0,#FIQ_STACK_SIZE
msr CPSR_c,#MODE_IRQ|I_BIT|F_BIT // IRQ Mode
mov sp,r0
sub r0,r0,#IRQ_STACK_SIZE
msr CPSR_c,#MODE_SVC|I_BIT|F_BIT // Supervisor Mode
mov sp,r0
sub r0,r0,#SVC_STACK_SIZE
msr CPSR_c,#MODE_SYS|I_BIT|F_BIT // System Mode
mov sp,r0
// Copy initialized data to its execution address in RAM
// -----------------------------------------------------
#ifdef ROM_RUN
ldr r1,=_etext // -> ROM data start
ldr r2,=_data // -> data start
ldr r3,=_edata // -> end of data
1: cmp r2,r3 // check if data to move
ldrlo r0,[r1],#4 // copy it
strlo r0,[r2],#4
blo 1b // loop until done
#endif
// Clear .bss
// ----------
mov r0,#0 // get a zero
ldr r1,=__bss_start // -> bss start
ldr r2,=__bss_end__ // -> bss end
2: cmp r1,r2 // check if data to clear
strlo r0,[r1],#4 // clear 4 bytes
blo 2b // loop until done
/*
Call C++ constructors (for objects in "global scope")
ctor loop added by Martin Thomas 4/2005
based on a Anglia Design example-application for ST ARM
*/
LDR r0, =__ctors_start__
LDR r1, =__ctors_end__
ctor_loop:
CMP r0, r1
BEQ ctor_end
LDR r2, [r0], #4
STMFD sp!, {r0-r1}
MOV lr, pc
MOV pc, r2
LDMFD sp!, {r0-r1}
B ctor_loop
ctor_end:
// Call main program: main(0)
// --------------------------
mov r0,#0 // no arguments (argc = 0)
mov r1,r0
mov r2,r0
mov fp,r0 // null frame pointer
mov r7,r0 // null frame pointer for thumb
ldr r10,=main
mov lr,pc
bx r10 // enter main()
/* "global object"-dtors are never called and it should not be
needed since there is no OS to exit to. */
.size _start, . - _start
.endfunc
.global _reset, reset, exit, abort
.func _reset
_reset:
reset:
exit:
abort:
#if 0
// Disable interrupts, then force a hardware reset by driving P23 low
// -------------------------------------------------------------------
mrs r0,cpsr // get PSR
orr r0,r0,#I_BIT|F_BIT // disable IRQ and FIQ
msr cpsr,r0 // set up status register
ldr r1,=(PS_BASE) // PS Base Address
ldr r0,=(PS_PIO) // PIO Module
str r0,[r1,#PS_PCER_OFF] // enable its clock
ldr r1,=(PIO_BASE) // PIO Base Address
ldr r0,=(1<<23) // P23
str r0,[r1,#PIO_PER_OFF] // make sure pin is contolled by
PIO
str r0,[r1,#PIO_CODR_OFF] // set the pin low
str r0,[r1,#PIO_OER_OFF] // make it an output
#endif
b . // loop until reset
.size _reset, . - _reset
.endfunc
.end
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Posted on:
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You have not really explained your problem, or how it relates to C++, or the ISR (you only posted assembler!). You have only posted the startup code, what makes you think the problem is there, all the issues you mentioned appear to be related to code you have not posted. What can we say!? If using global objects, then the startup must invoke the constructors for those (and any static objects). Your start up does that. The order in which global objects are are constructed is undefined, so each one must be self contained and not depend on any other being defined. If a global object is accessed in the ISR, any access to that global must either be atomic, or uninterruptable. Also any variables shared between the interrupt and normal context or between separate threads must be declared volatile. Clifford
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