WRITECODE stores wrong 14-bit word values in FlashMEM

[BobPigford]

Hello all!

Following Darrel Taylor's excellent instructions, I was careful to WRITECODE to 4 word (complete) blocks starting at $1800 (or any other address where the two LSBs are 0's). I still saw wrong stored values. Every 6th address (and a few others) had an error ... VERY strange behavior.

I had been using 12 WORD sized array variables of 3 elements each, stuffing the last 2 variables of each array into memory (WRITECODE). Suspecting that array variables were the culprits, I changed to 36 individual WORD variables along with all the repetitive code required. NOW IT WORKS!

The PBP manual (pg 25) says clearly that "The compiler will assure that arrays, as well as simple variables, will fit in memory before successfully compiling."

My code is about 4100 WORDs in size. It compiled just fine, albiet showing three notes at the bottom of the screen that code page boundaries were being crossed. I had assumed that since the code compiled just fine, that the 3 warnings pertained to the overall size of my code. BUT, perhaps those were warnings that arrays would not work.

BUT why did it still compile OK? Did the PBP compiler let me down?

Makes me wary of using array variables. I need to learn more about this in the future!

Thanks again to all for your help!
Bob Pigford
Newark, Delaware

[Darrel Taylor]

Great! Glad it helped.

Makes me wary of using array variables.

Nothing to worry about there. Arrays work perfectly with PBP.
And yes, PBP makes sure the arrays will fit in a BANK of RAM.

The crossing boundary warnings refer to the FLASH memory used by the program. The same area of memory that you are WRITECODEing to.
Arrays can not cause that warning.

Array indexes always start at 0.
So if you have a word array of 3 elements, the index goes from 0 to 2.
It's easy to forget and try to use 1 - 3, but 3 would be outside of the array, probably a RAM location used by another variable.

PBP does not do any "Range Checking". It's up to you to stay within the bounds of the array.

Just about any good program will use arrays in some form or another.
So yup, time to learn ... then play ... then learn more ...
<br>

[rsocor01]

Darrel,
From reading other posts and other documentation (if I understood them correctly) when using arrays in a pic16fxxx and if the program crosses the memory boundary then that would be looking for trouble. In other words, if you are using arrays all over the place in your program, then your program has to fit in one memory block which is ussually not the case. Otherwise, the program won't work properly.
I personally like arrays. They make your program looks neat and more profesional, but also my programs are usually bigger than 2K.

Any comments on this?

Robert

[Darrel Taylor]

NO! Not true at all.

The size of your program has NO effect on arrays.
Arrays are in RAM, the program is in FLASH.

You may be thinking of the problems that can happen with the BRANCH command if the code is larger than 2K. In which case you need to use BRANCHL.

[BobPigford]

Darrel, et al,

I understand going out of bounds of a dimensioned array, and that arrays start at 0. I believe that my use of array variables was correct, but I will go back and look again. Perhaps I missed something.

I am glad to hear that PBP did not let me down, per se, as array variables are held in RAM and arrays crossing any page boundaries are handled by PBP.

So, I guess I will have to go back and bang out the code with array variables again. It may be a while, but I will report back.

Thanks to all for your help!
Bob Pigford
Newark, DE, USA

[BobPigford]

I am glad to hear that PBP did not let me down, per se, as array variables are held in RAM and arrays crossing any page boundaries are handled by PBP.

Oops. I should not have talked about arrays crossing any boundaries since Darrel reminded me that they are in RAM. Sorry.

Bob

[rsocor01]

Darrel,
I think my confusion comes from the PicBasic Pro Manual, section 4.5, "Arrays".
"Arrays must fit entirely within one RAM bank on 12-bit, 14-bit or pic17cxxx devices."

Yeap, I know the program is not stored in RAM. But, what are the implications of this limit to one RAM bank for arrays? Would it be only the limited number of elements in an array?

Robert