Compiler/TDA2EXEVM: Regarding Exception Handler in MPU A15

Hi Harshalkumar,

I have forwarded your question to an expert for comment.

Regards,
Yordan

Hi Harshal,

Could you please help me understand the problem a bit better?

Are you currently no receiving the exception (code does no jump to the exception handler at all)?

or

You are receiving the exception but on the execution of a different instruction?

Thanks and Regards,

Piyali

Hello Priyali,

In case of SVC exception it working properly. but if I try to generate Exception on Divide by Zero instruction it can not generate any exception after execution of divide by zero instruction. As per doc it should goes to undefined exception. Code does no jump to the exception handler at all.

Thanks

Hi Harshal,

I will try and reproduce this problem at my end and keep you updated on what I find.

Thanks and Regards,
Piyali

Just to add:
Cortex A15 supports ARMv7-A architecture.

Thanks and Regards,
Piyali

Hello Priyali,

Thanks for the reply.

Please suggest any scenario or instruction that generate any exception i.e. Abort or Data Abort or Undefined to check exception handling.

Hello Piyali,

Thanks for the reply. This instruction solve our problem of exception generation. 

Hello Piyali,

I have some issue in that instruction, If controller is in Thumb mode before execution of instruction, control goes to FIQ exception and if i change it to ARM mode manually before that instruction, control goes to Undefined Exception.

If I try to change Thumb to ARM mode by writing to CPSR in application, control goes to previous instruction again and can not generate any exception.

while(GIsr0Count != 1)
{
}
ASM("mrs R0,cpsr");
ASM("and R0,#0xFFFFFFDF");
ASM("msr cpsr,r0");
asm volatile (".word 0xe7f000f0\n");
GIsr0Count = 2;

162 while(GIsr0Count != 1)
403055fc: BF00 nop
403055fe: F645233D movw r3, #0x5a3d
40305602: F2C40330 movt r3, #0x4030
40305606: 781B ldrb r3, [r3]
40305608: B2DB uxtb r3, r3
4030560a: 2B01 cmp r3, #1
4030560c: D1F7 bne #0x403055fe
169 ASM("mrs R0,cpsr");
4030560e: F3EF8000 mrs r0, apsr
170 ASM("and R0,#0xFFFFFFDF");
40305612: F0200020 bic r0, r0, #0x20
172 ASM("msr cpsr,r0");
40305616: F3808900 msr cpsr_fc, r0
4030561a: 00F0 lsls r0, r6, #3
4030561c: E7F0 b #0x40305600
175 GIsr0Count = 2;


when the controller is in Thumb mode following code is generated, it can not generate the suggested udf #0 instruction

while(GIsr0Count != 1)
{
}
asm volatile (".word 0xe7f000f0\n");
GIsr0Count = 2;

162 while(GIsr0Count != 1)
403055fc: BF00 nop
403055fe: F6452331 movw r3, #0x5a31
40305602: F2C40330 movt r3, #0x4030
40305606: 781B ldrb r3, [r3]
40305608: B2DB uxtb r3, r3
4030560a: 2B01 cmp r3, #1
4030560c: D1F7 bne #0x403055fe
4030560e: 00F0 lsls r0, r6, #3
40305610: E7F0 b #0x403055f4
175 GIsr0Count = 2;

please suggest why controller behave different in different mode also provide some detail that we are able to generate undefined exception without manually change.