Mathematics and remainder for PLL MC145158

[Darrel Taylor]

R2 is one of PBP's system variables. They are defined in the PBPPICxx.RAM files, located in the PBP folder.

In this case R2 holds the modulas (remainder) of the DIV32 command.

For more info ... http://www.picbasic.co.uk/forum/showthread.php?t=48

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[CocaColaKid]

So this is basically the same as the // but only for DIV32?

[Darrel Taylor]

Correct!<br><br>

[CocaColaKid]

On that note though would you not think that it would be listed as a reserved word?

[rhino]

R2 is one of PBP's system variables. They are defined in the PBPPICxx.RAM files, located in the PBP folder.

In this case R2 holds the modulas (remainder) of the DIV32 command.

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I was looking through this file, hoping to learn some of that voodoo that Darrel pops on us time to time... but all the definition said was "System Register". Does anyone know just what exactly these other variables mean or do? Is it documented somewhere that I have missed?

[Darrel Taylor]

I've been found out. I guess I can take those pins out of my Rhinoceros doll now.

While the PBPPICxx.RAM declares the system variables, the PBPPICxx.LIB and PBPPICxx.MAC files are where you'll find out how they are used.

For instance, with the DIV32 command on an 18F part... Open up the PBPPIC18.LIB file and search for DIV32. You'll find this header in front of the code for the DIV32 command.

;************************************************
;* DIV32      : 31 x 15 divide
;*                                    
;* Input      : R0, R2 = 32 bits 
;*            : R1 + 1, W = divisor
;* Output     : R0 = quotient    
;*            : R2 = remainder      
;*                                        
;* Notes      : Uses result from MUL. 
;************************************************

From that you can see that R2 is the remainder of a DIV32, even though it's not mentioned anywhere in the manual.

Most of the PBP macros have a header showing the input and output variables, but not necessarily all the system variables that are used by that routine. For that you have to digest the code and follow subroutine calls.

As far as I know, there is no list of macro's or the system variables that they use. My guess is that it would create a tech support nightmare for them if they put that kind of stuff in the manual. Can't blame them.

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[rhino]

aaaahhh..... it's a dark mysterious art. I shall take your teachings and proceed with caution. As for the pins.... I'll consider it some kind of hazing/right of passage ritual. Seriously... thanks for the info.