Interrupts on a PowerPC

g

le

If you are asking about the method to invoke the function that you have written by using IVT, then you have to have a jump to that address in the IVT if the routine is big else, you can code it there itself.

Karthik Balaguru

Here is a sample from a uCOS RTOS gcc port for the mpc555. This decrementer code may be slightly more complicated than you need because it adjusts for decrementer overflow to keep the tick in sync with real time.

Scott

/*

****************************************************************************************************

• OS_Set_decrementer

**************************************************************************************************** */ void OS_Set_decrementer (void) { __asm__ volatile (" lis r4, dec_init@ha "); __asm__ volatile (" lwz r4, dec_init@l(r4) "); __asm__ volatile (" mfdec r5 "); /* compensate for interrupt latency by */ __asm__ volatile (" add r5,r4,r5 "); /* adding decrementer underflow */ __asm__ volatile (" cmplw r4,r5 "); /* prevent that the compensated value is */ __asm__ volatile (" bge DEC_SetReg "); /* greater than the original */ __asm__ volatile (" mr r5,r4 "); __asm__ volatile ("DEC_SetReg: "); __asm__ volatile (" mtdec r5 "); /* load Decrementer */ }

/*

****************************************************************************************************

• DEC_Hdlr

**************************************************************************************************** */ void DEC_Hdlr (void) { OS_CPU_SR cpu_sr;

OS_ENTER_CRITICAL(); OS_Set_decrementer (); OS_EXIT_CRITICAL();

OSTimeTick (); /* process tick */ }

Hello,

how does the microcontroller know that the void DEC_Hdlr routine should be executed? There must be a handler.s file like this:

#handler.s

.equ  INTC_IACKR, 0xfff48010  # Interrupt Acknoledge Register address .equ  INTC_EOIR,  0xfff48018  # End Of Interrupt Register address

.extern DEC_Hdlr

IVOR10Handler: bl DEC_Hdlr rfi

#eof

is that correct? Correct me if something is missing.

Regards, Gilles

Not Really Me wrote:

**************************************************************************************************** **************************************************************************************************** **************************************************************************************************** ****************************************************************************************************

Hello, do you have an example how to write the address of a C-function into the IVT?

Regards, Gilles

karthikbalaguru wrote:

**************************************************************************************************** **************************************************************************************************** **************************************************************************************************** ****************************************************************************************************

Sorry, was in a rush. Of course you are right. Here is the .s code. BTW, prologue and epilogue are macros that save and restore the stack frame. Remember that this example is uC/OS-II specific. You may have to adjust. Send me a direct email and I will send you the files.

Scott

decIsr:

prologue

bl OSIntEnter

lis r11,OSIntNesting@ha lbz r0,OSIntNesting@l(r11) cmpwi r0,1 bne DEC_Intr_NotSaveSP

# Get pointer to current TCB lis r11,OSTCBCur@ha lwz r11,OSTCBCur@l(r11)

# Save stack pointer in current TCB stw r1,0(r11)

DEC_Intr_NotSaveSP: bl DEC_Hdlr

bl OSIntExit

epilogue

**************************************************************************************************** **************************************************************************************************** **************************************************************************************************** ****************************************************************************************************

Hello,

I've found the missing part to get my code working:

First one has to define a line like this (ass shown in AN3524SW): /* Interrupt Handler Parameters */ __IV_ADDR = ADDR(.xcptn);

in the linker file.

Then this must be added in handler.s: .equ IV_ADDR, __IV_ADDR .org IV_ADDR

because the ISR must be close together.

Somewhere in the code (during the initialization) the addresses of the ISR must be written into the corresponding special function registers: asm ("lis r5, __IV_ADDR@h"); asm ("mtivrp r5 "); asm ("lis r5, IVOR10Handler@h"); asm ("ori r5, r5, IVOR10Handler@l"); asm ("mtivor10 r5");

Regards, Gilles