Program fails crossing code page

[Darrel Taylor]

variable blabla = 0
was asmed to clrf statements because the last time I checked,
PBP zeros variables by copying a zero value to the variable like any other value,
wasting one instruction per "variable = 0" statement.

No, PBP will use CLRF when zeroing a variable.

That ISR is from the original Elapsed Timer Demo, in which I had declared the variables without bank assignments, letting PBP assign the banks as needed.

By changing Seconds = Seconds + 1 to incf _Seconds,F, you have bypassed PBP's banking mechanism and it's likely you are overwriting other variables in RAM.
The few bytes that were gained, were probably the instructions changing banks.

If you declare the variables as BANK0 it would be ok.
Or if you put them back to PBP statements it will be ok.

[Art]

Nice to hear! Given I haven't tried it yet.
Does var = var + 1 translate to an incf instruction?
Maybe that is what I'm trying to remember...
It was years ago, I disassembled a PBP program
With the tool in ICprog for 16F84.

Great news anyway if I don't have to drop anything fancy
To gain space. Thanks

[Darrel Taylor]

Yes, var = var + 1 turns into an incf.

Here's a small program ...

B   VAR BYTE
W   VAR WORD

B = 0
W = 0

B = B + 1
W = W + 1

After compiling, a quick look in the .LST file reveals all.

                      00107 ; C:\PIC\ART\ASMVSPBP.PBP       00014   B = 0
                      00108         MOVE?CB 000h, _B
  00000000                M PREV_BANK = 0
0001   01BA               M         clrf    _B
                      00109 
                      00110 ; C:\PIC\ART\ASMVSPBP.PBP       00015   W = 0
                      00111         MOVE?CW 000h, _W
  00000000                M PREV_BANK = 0
0002   01B8               M         clrf    _W
  00000000                M PREV_BANK = 0
0003   01B9               M         clrf    (_W) + 1
                      00112 
                      00113 ; C:\PIC\ART\ASMVSPBP.PBP       00017   B = B + 1
                      00114         ADD?BCB _B, 001h, _B
  00000000                M PREV_BANK = 0
0004   0ABA               M         incf    _B,   F
                      00115 
                      00116 ; C:\PIC\ART\ASMVSPBP.PBP       00018   W = W + 1
                      00117         ADD?WCW _W, 001h, _W
  00000000                M PREV_BANK = 0
0005   0AB8               M         incf    _W,   F
0006   1903               M         btfsc   STATUS, Z
0007   0AB9               M         incf    (_W)   + 1, F

[Art]

Ah, nice to know. It looks like there was a time when this wasn't the case:
http://www.rcfaq.com/PIC/optimize.htm
Although incrementing a variable shouldn't have ever used three words unless a clrwdt was thrown in as well.

[Darrel Taylor]

That page has been pointed to several times around here.
It's probably the worst examples of PBP programming found anywhere on the internet.

Sure, the programs are smaller when you use some of those techniques.
But the savings come from bypassing the normal bank switching and page bit setting that PBP does to insure everything keeps working properly.

The examples are fine by themselves because they are never larger than 2K and variables are never outide of bank0.
But when you try to use them in your program that is bigger with more variables, all hell breaks loose.

There are a couple true statements on the page, but with so much bad advice, it's hard to find them?

My advice is to delete that bookmark from your favorites, and forget what you read.

In his defense, ... it was 2002. I had some strange ideas about PBP back then too.

[Art]

Haha, It was likely intended to apply to 1-2K pics!

Um, all hell did break loose. The ISR routine was the problem BTW.

It's probably the worst examples of PBP programming found anywhere on the internet.

Maybe I need to post some code to claim that title.