Assembly Language inside PBP

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- 11th October 2009, 11:23
Bill Legge

Assembly Language inside PBP

I'm using PBP with a PIC18F1220 in a weather station.
The rain gauge - a tipping bucket - triggers an assembler interrupt routine that accumulates the number of bucket tips.

the variable (in PBP) that holds the count is:

Rain VAR WORD

And the ASM interrupt routine includes the instruction:

incf _Rain ; Increment Rain variable

all works OK but the asm does not recognise the variable 'Rain' as a WORD and 'rolls over when it reaches 255.

How do I get the asm interrupt routine to deal with 'Rain' as a WORD

Thanks
Bill Legge
- 11th October 2009, 12:10
Jerson

You can try this.

movlw 1
addwf _Rain ; increment the LSB
btfsc STATUS,C ; if overflow, increase MSB
incf _Rain+1
- 12th October 2009, 08:59
Bill Legge

BYTE/WORD in Assembler

Thanks Jerson - I will give it a go.

I presume that PBP allocates two BYTES of memory to the WORD sized variable 'RAIN' and the assembler routine only deals with one of them?

I guess I could create two BYTES to hold the RAIN data and increment the 'higher' BYTE if there is a carry from the 'lower' - Seems a bit cumbersome and I was looking for a neater/easier way.

Regards Bill Legge
- 12th October 2009, 09:13
Acetronics2

Quote:

Originally Posted by Bill Legge

Seems a bit cumbersome and I was looking for a neater/easier way.

Hi, Bill

As the 18F1220 is a 8 bits processor ... the neater/easier way is to use a 16 bits device !!!

not obvious easier, eh ???

NOW, The "DT Instant interrupts" might do the trick " neater " ( sic ) ... it's not raining as the "Niagara falls" , after all ...

OR use one of the chip 16 Bits counters ... you have 3 aboard, after alll ...

Alain
- 12th October 2009, 21:52
Darrel Taylor

Quote:

Originally Posted by Bill Legge

I guess I could create two BYTES to hold the RAIN data and increment the 'higher' BYTE if there is a carry from the 'lower' - Seems a bit cumbersome and I was looking for a neater/easier way.

Simple addition or incrementing variables doesn't use the system registers.
So it's ok to break out of ASM and do it with PBP.

Code:

Rain VAR WORD ASM MyInt ;save context ;asm part here ENDASM Rain = Rain + 1 ASM ;more asm here ;restore context retfie ENDASM