Re: [OT] Some pic asm code help

["Frank Mc Alinden" <frankmc@xxxxxxxxxxxxxxxx>]

Hi Stephen

Thanks for clearing that up .......
Any ideas on how i go about to writing code to multiply the result (445) by
15.625uV....???

Thanks again

Frank


----- Original Message -----
From: "Stephen McGarry" <Selfbuild@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Tuesday, September 11, 2007 5:01 AM
Subject: Re: [ukha_d] [OT] Some pic asm code help


> Hi Frank
> when you rotate RRF DS_DATA1 the least significant bit goes into the
carry
> bit
>    +---+    +----------+
> +-> C ---> Register >-+
>   +---+    +----------+
> +-------<---------<-------+
>
> then when you RRF DA_DATA0 this bit is rotated from the carry into the
> Most sig bit of the LSB
>
> i.e.
> MSB =11110010 and LSB =00011000 from your example of F218h
> first  RRF MSB =X1111001 with C=0 then RRF LSB giving 00001100 (X=is
> unknown value)
> second RRF MSB =1X111100 with C=1 then RRF LSB giving 10000110
> third  RRF MSB =00X11110 with C=0 then RRF LSB giving 01000011
> The test bit 4 of MSB it 1 so convert
> COMF MSB =11100001 COMF LSB =10111100
> then add 1 to give MSB = 11100001 and LSB=10111101
>
> mask off top 4 bits of MSB to 00000001
> Giving final value of 0000000110111101 = 445 (as shown by Ian D)
>
> Does this help
> Stephen
>
> P.S. does your development system allow you to single step through the
> code?
> if so check registers at each step for the above values
> (inserting the known starting values into DA_DATA at the start of the
> debugging.)
>
>
> Frank Mc Alinden wrote:
>>
>>
>> Hi Stephen
>>
>> Loaded your code but still no joy ..it gave me a reading of around
3mV
>> ...??/
>>
>> I dont understand how your code shifts the bits from the MSB byte
>> DS_DATA1
>> into the LSB byte DS_DATA0....
>>
>> Thanks for your help
>>
>> Frank
>>
>> ----- Original Message -----
>> From: "Stephen McGarry" <Selfbuild@xxxxxxx
>> <mailto:Selfbuild%40Stocksons.co.uk>>
>> To: <ukha_d@xxxxxxx <mailto:ukha_d%40yahoogroups.com>>
>> Sent: Monday, September 10, 2007 5:57 AM
>> Subject: Re: [ukha_d] [OT] Some pic asm code help
>>
>>  >I see an immediate problem in the code as you are SUBTRACING
the mask
>> not
>>  >ANDing !
>>  > and you can make the rotates a lot simpler... (without
firing up my
>>  > simulator and checking)
>>  >
>>  > HTH Stephen
>>  >
>>  > Try this :-
>>  >
>>  > CEL2760
>>  > ;rotate both (don't worry about carrys into MSB as you will
mask
>> later)
>>  > rrf DS_DATA1,1 ;shift down MSB and move bit into carry
>>  > rrf DS_DATA0,1 ;then move it into the LSB and move it down
>>  > rrf DS_DATA1,1 ;and again
>>  > rrf DS_DATA0,1
>>  > rrf DS_DATA1,1 ;and again
>>  > rrf DS_DATA0,1
>>  >
>>  > btfss DS_DATA1,4 ;check sign status
>>  > goto mask_up_nib ;
>>  >
>>  > comf DS_DATA1,1 ;yes , 2,s compliment
>>  > comf DS_DATA0,1 ;invert and
>>  > incf DS_DATA0,1 ;add 1
>>  >
>>  > btfsc C_bit ;
>>  > incf DS_DATA1,1 ;
>>  >
>>  > mask_up_nib
>>  > movlw 0fh ;mask out rubbish
>>  > andwf DS_DATA1,1
>>  >
>>  > cely return ;
>>  >
>>  > Frank Mc Alinden wrote:
>>  >>
>>  >>
>>  >> Hi Ian
>>  >>
>>  >> I forgot to rotate the MSB so those values in my last
post are way
>>  >> out....
>>  >> try these MSB D2h .....LSB BBh................MSB
D1h.....LSB F0h
>>  >>
>>  >> Heres a copy of my current code which is suppose to
convert the raw
>> dat
>>  >> to
>>  >> 16 bit
>>  >>
>>  >> Thanks agian
>>  >> Frank
>>  >>
>>  >> CEL2760
>>  >>
>>  >> bcf neg ;clear negative flag
>>  >> btfss DS_DATA1,7 ;negative ? if yes , skip next
>>  >> goto cel2 ;no
>>  >>
>>  >> bsf neg ;set negative flag
>>  >>
>>  >> cel2 ;rotate LSB
>>  >>
>>  >> bcf C_bit ;clear carry flag
>>  >> rrf DS_DATA0,1 ;Data0 holds LSB data (0F)
>>  >>
>>  >> bcf C_bit ;clear carry flag
>>  >> rrf DS_DATA0,1 ;
>>  >>
>>  >> bcf C_bit ;clear carry flag
>>  >> rrf DS_DATA0,1
>>  >>
>>  >> ;SHIFT AND ROTATE MSB
>>  >>
>>  >> chec_msb_bit0
>>  >> btfss DS_DATA1,0 ;Check MSB Byte bit 0
>>  >> goto set_lsb_5_lo ;
>>  >> bsf DS_DATA0,5 ;set bit 5 of lsb byte
>>  >> goto chec_msb_1 ;
>>  >>
>>  >> set_lsb_5_lo
>>  >> bcf DS_DATA0,5 ;
>>  >>
>>  >> chec_msb_1
>>  >>
>>  >> btfss DS_DATA1,1 ;Check MSB Byte bit 1
>>  >> goto set_lsb_6_lo ;
>>  >> bsf DS_DATA0,6 ;set bit 6 of lsb byte
>>  >> goto chec_msb_2 ;
>>  >>
>>  >> set_lsb_6_lo
>>  >> bcf DS_DATA0,6 ;
>>  >>
>>  >> chec_msb_2
>>  >> btfss DS_DATA1,2 ;Check MSB Byte bit 2
>>  >> goto set_lsb_7_lo ;
>>  >> bsf DS_DATA0,7 ;set bit 7 of lsb byte
>>  >> goto shift_data1 ;
>>  >>
>>  >> set_lsb_7_lo
>>  >> bcf DS_DATA0,7 ;
>>  >>
>>  >> shift_data1
>>  >>
>>  >> bcf DS_DATA1,0 ;
>>  >> bcf DS_DATA1,1 ;
>>  >> bcf DS_DATA1,2 ;
>>  >>
>>  >> bcf C_bit ;clear carry flag
>>  >> rrf DS_DATA1,1 ;
>>  >>
>>  >> bcf C_bit ;clear carry flag
>>  >> rrf DS_DATA1,1 ;
>>  >>
>>  >> bcf C_bit ;clear carry flag
>>  >> rrf DS_DATA1,1 ;
>>  >>
>>  >> btfss neg ;check sign status
>>  >> goto mask_up_nib ;
>>  >>
>>  >> comf DS_DATA1,1 ;yes , 2,s compliment
>>  >>
>>  >> comf DS_DATA0,1 ;yes , 2,s compliment
>>  >> incf DS_DATA0,1 ;
>>  >>
>>  >> btfsc C_bit ;
>>  >> incf DS_DATA1,1 ;
>>  >>
>>  >> mask_up_nib
>>  >>
>>  >> movlw 0fh ;mask upper nibble
>>  >> subwf DS_DATA1,1 ;
>>  >>
>>  >> cely return ;
>>  >>
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