Lpc2000

--- In lpc2000@yahoogroups.com, "friese99de" <jens.hildebrandt@e...> 
wrote:
> Hi,
> 
> I just came across this group because I have a problem similar to 
that
> of the OP. Did you find a solution meanwhile? 
> I'm using gcc 3.2.1 under cygwin and tried to build the blinky_irq
> example for a LPC2106. Since it didn't work I stripped the program
> down to a bare endless loop in main() and a timer ISR that toggles a
> LED an GPIO24. After approx. 3min. the LED stops toggling and I get 
an
> Abort exception. A look at the disassembled code showed that gcc is
> messing up the stack pointer in IRQ mode, losing some words every 
time
> the ISR is invoked.
>  The code looks the following way:
> 
> 00000278 <tc0>:
>  278:	e52dc004 	str	ip, [sp, -#4]!
>  27c:	e1a0c00d 	mov	ip, sp
>  280:	e24ee004 	sub	lr, lr, #4	; 0x4
>  284:	e92dd80c 	stmdb	sp!, {r2, r3, fp, ip, lr, pc}
>  288:	e24cb004 	sub	fp, ip, #4	; 0x4
>  28c:	e3a0320e 	mov	r3, #-536870912	; 0xe0000000
>  290:	e283390a 	add	r3, r3, #163840	; 0x28000
>  294:	e5933000 	ldr	r3, [r3]
>  ... some load and store operations on GPIO registers with r2, 
r3 ...
>  2e0:	e3a02000 	mov	r2, #0	; 0x0
>  2e4:	e5832000 	str	r2, [r3]
>  2e8:	e95b980c 	ldmdb	fp, {r2, r3, fp, ip, pc}^
> 
> As you can see, in the beginning registers are saved on the stack 
thus
> decrementing sp. BTW, the way ip is saved in the beginning is
> pointless since ip is not restored from that location upon ISR exit.
> At the end, registers are restored from stack using fp as base
> pointer. The pc is loaded with the adjusted return address and
> simultaneously cpsr is restored from spsr_irq. Sp however is not
> restored so that at ISR exit sp is seven words lower than at ISR
> entry.
> Either I missed some point when building the program (e.g. forgot
> certain gcc options) or gcc 3.2.1 is buggy here.
> Options I use are  "-mcpu=arm7tdmi -gstabs" for the assembly of
> startup.s and "-c -g -I. -mcpu=arm7tdmi" for compiling of C-source
> files. Linker options are "-T Flash.ld -nostartfiles -Lgcc -L.", 
where
> Flash.ld is the linker script supplied with Keil's blinky_irq 
example
> adjusted to the actual Flash and RAM sizes of the LPC2106.
> Has anybody else in the group encountered similar problems and if 
so,
> have you found a solution?

The interrupt entry and exit code in gcc 3.2.x and older doesn't 
work.  Either upgrade to gcc 3.3.x, where it works, or write the 
entry/exit code yourself.

Regards,
Karl Olsen