Where is my procedure called from?

[jamesjl]

Hi all,

I have a sizeable program that is misbehaving. A subroutine within the program is explicitly called from 5 locations throughout the code, however, certain (apparently random) conditions appear that call this routine from an undetermined location. I have used printf statements to try and see where the routine is being erroneously called from, but with no luck. Is there any way of determining where this routine is being called from, e.g. looking at the stack, etc?

Any help would be much appreciated.

Regards,

Jason

[Ttelmah]

The stack will only help if the routine is 'called'. If it is jumped to, then there will be no record.
Now the compiler is now pretty good at not generating this sort of problem, so one has to ask what is causing it?. What is the chip?. There have been a number of faults in the past with particular processor variants, which have problems with a call/jump, if it crosses a page boundary. One 'classic' example, was the 18Fxx2 chips, which for about the first two years, did this. CCS has the ability to insert the 'fix' for this error (it can be enabled in the device editor if you have this), and till a few months ago, did this by default. However since the latest couple of chip versions, don't have this problem, the default is now to disable this fix.
I'd start by looking at the errata sheets for the chip concerned, and see if there is anything of this sort. If not, then you either need to be using an ICE, with a 'track back' ability (most hardware ICE systems can do this), or are going to have to find the error by searching the list file. If you think the program is getting to the start of the routine, a simple search of the listing, for the address of this point, will find every location that references it.

Best Wishes

[Mark]

If you are using a PIC16 and const arrays, then this sort of behaviour will happen if you exceed the array limits. There are no bounds checks and the method for "returning" values could cause the program to jump to a location that is expectiing a retlw but instead jumps into other parts of the code.

The 'track back' ability that RJ refers to is also known as 'trace'. An ICE would be great for this but not everyone has one. Another option is to make your code run on the MPLAB simulator and use its trace ability. I have done this in the past when I didn't want to get out the ICE. If your program relies on external events, you might have to fudge them with a bit of code to make your application run.

[PCM programmer]

[jamesjl]

HI All,

I think I found it. Whilst I thought that the routine was being called in error, I was wrong. I found another location that could call it and things are now starting to behave.

I am using an 18F4585 and an 18F6680 in my project and I need interrupt driven CAN capability. Could someone tell me what the maximum stack depth is for an 18F series PIC?

Can anyone recommend an good mid-range ICE? The project I am working on is starting to be large enough to warrant one now. Do they work with the CCS IDE or do I have to use MPLAB. I have CCS PCWH and am about to download the latest version. Does anyone have a paper on how to convert my project to compile using MPLAB?

Many thanks,

Jason

[Mark]

I'd get the ICE4000

The stack depth is in the datasheet but it should be 32.

There is no paper needed to convert. Just start a project in MPLAB. It will ask you the PIC, the tool suite. Then you just add your main C file to the IDE and you are done. Do not add all the C files under source. It will try to compile each of them. You can add them under the other files though. Make sure that you have downloaded the CCS plugin and installed that. You can find it on their website.

[jamesjl]

Mark,

will the ICE 4K work with the C compiler IDE or just MPLAB? Does it work with C code? Does anyone else have an opinion on getting an ICE?

Thanks,

Jason.

[Mark]

Chances are, the ICE that you use will have an IDE that goes with it. I don't have the CCS IDE so if it is not listed as a debug device, then it probably will not work. That's why I like the Microchip stuff. I can use the ICD2, Promate, ICE2000, ICE4000, simulator, compiler all within MPLAB. C code is compiled and eventually converted to asm code. This is really what goes into the ICE. Machine instructions and not a high level language. But from your point of view. Yes you can write C language, compile and then run with the ICE.

[jamesjl]

Mark,

many thanks for the information. I'm sure to find it useful when I get around to getting an ICE. It's budget time at the office, so I'll be sure to put in a request for one. One final thing; can I use the CCS ICD with MPLAB?

Regards,

Jason

[Mark]