const int16 array low byte only with TinyBLD

peter_dufault · Joined: 25 Jul 2006 Posts: 6

My system is: 18F4620, 20 MHz, CCS PCWH 3.249.

I've been working on it for some time, and I just started to add in the bootloader. I searched around and tried the TinyBLD bootloader, and it seemed to work very easily right away. However, my program does not operate properly when loaded using the bootloader. It looks like the main problem is that reads from a const int16 array only return the low byte.

Here are bits of my code along with the output:

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Can you provide a test program instead of code fragments ?
Post something that I can drop right into MPLAB and punch the
compile button, and it will compile. Then I can look at the .LST
file and see what's happening. Make sure the program is very
small -- no more code than what you've already posted.

peter_dufault · Joined: 25 Jul 2006 Posts: 6

I put together an example that I expected would illustrate the problem, except that the test functioned as I wanted the original program to! Very disappointing.

I then spent the next 10 hours taking apart the program to see if the problem would be exposed in some other way. I don't have a clean example yet, but I can make it work or not work by enabling or disabling small sections of code.

At this time it seems like the problem is sensitive to other accesses to 16 bit variables. Additionally, there may be a sensitivity to the presense of interrupt handlers, even if the contents of them are empty. There also seems to be something going on with the configuration fuses.

I will continue to work on an example as compact as possible to exercise this problem. It's 2:00 am. I will get back to this in the morning.

Ttelmah · Guest

An 'empty' interrupt handler, can be a killer. Always put a 'dummy' function (like 'delay_cycles(1)'), into such a handler if declared. When you 'call' the interrupt handler, the compiler adds the code to clear the interrupt at the end of the handler. If there is no code at all in the handler, this can get missed...

Best Wishes

peter_dufault · Joined: 25 Jul 2006 Posts: 6

Well, I may have tracked down the problem. Eventually I got to where I would turn the problem on or off depending on how much code I commented out. It didn't really matter which code was removed. I wondered if there was a fuse issue. I had seen this thread: http://www.ccsinfo.com/forum/viewtopic.php?t=26242

which gave a clue about the EBTRB control bit in CONFIG7. It is the "Boot Block Table Read Protection bit" for 0x0 to 0x7FF. Note that it is active low to enable protection. In looking to how the fuses were set by the bootloader:

Gabriel Caffese · Joined: 09 Oct 2003 Posts: 39 Location: LA PLATA, ARGENTINA

Peter_dufault,

Tinybootloader doesn�t allow you to change fuses !!
You set them once, when programming Tinybootloader in 18F4620.
If you read the PIC fuses after updating code with the bootloader, you�ll see they are just the same that when programmed the PIC with the Tinybootloader, no matter what your code says.
Even with this, it�s the best one I�ve seen.

Gabriel.-

peter_dufault · Joined: 25 Jul 2006 Posts: 6

Gabriel,

Yes, actually, my post was unclear. The code I listed on July 26 was from the TinyBLD source for the 18F2620 (also used for the 18F4620). The error I found was with the original source: somehow, the _DEVID1 and _IDLOC0 fuses got included in there.