8-bit MicrocontrollersのトピックRe: CCR Interrupt Mask Bit in C?

CCR Interrupt Mask Bit in C?

BasePointer — Fri, 04 Apr 2008 16:39:17 GMT

Hi,

How can I move CCR to my local variable in C?

I have to test I bit:

void foo()

{

unsigned char before = CCR_I <---

DisableInterrupts;

....

if(before) EnableInterrupts;

}

10x

BP.

Message Edited by BasePointer on 2008-04-04 12:39 PM

Re: CCR Interrupt Mask Bit in C?

peg — Fri, 04 Apr 2008 17:56:09 GMT

Hi,

As the CCR is stacked you could use a method similar to that proposed here.
Or you could add a little assembly like this:

PSHA
TPA
STA variable
PULA

Re: CCR Interrupt Mask Bit in C?

fabio — Fri, 04 Apr 2008 17:59:12 GMT

Hi BP,

Try the __isflag_int_enabled() function. It returns true if I = 0.

void foo()

{

unsigned char before;
before = __isflag_int_enabled();

DisableInterrupts;

....

if(before) EnableInterrupts;

}

Ps.: this is in my new book

Best regards,

Message Edited by fabio on 2008-04-04 12:03 PM

Re: CCR Interrupt Mask Bit in C?

BasePointer — Fri, 04 Apr 2008 18:39:29 GMT

Hi fabio,

The code below works for me.

Code:

#include "intrinsics_hc08.h"void foo(void){  unsigned char before = __isflag_int_enabled();    DisableInterrupts; /* disable interrupts */  ..  ...  if(before) EnableInterrupts; /* enable interrupts */  }

Thank you so much.

BP.

Re: CCR Interrupt Mask Bit in C?

admin — Wed, 19 Dec 2012 10:03:04 GMT

Hi all,

I have a query regarding Z bit in CCR. When the following is performed,

a= 10

b=10

if (a==b), then Z flag should be set to TRUE.

However as soon as the instruction is executed the Z flag is cleared, when any other statements in the code is executed. There are no decision statements which is executed after this.

As I am from a testing background, I expect Z flag to be set to TRUE, until next comparison is performed.

Please help me out on this.

Thanks,

Dharani

Re: CCR Interrupt Mask Bit in C?

bigmac — Wed, 19 Dec 2012 12:05:56 GMT

Hello Dharani,

If you examine the reference manual for the device you are using, you should observe that a large proportion of the assembly instructions will affect the status of the Z-flag, not just the compare instructions.

You would seem to have two choices within your C code -

Do the comparison each time a branch decision is required.
Assign the comparison result to a variable, and then test the value within the variable for each decision.

For the latter method:

byte a, b, c;

...

c = (a == b); // Result is true or false

...

if (c) {

// Do something

}

Regards,

Mac