Using a WORD value in my Sx/B calculations

duffling

Im having trouble working out how to compute WORD values ..

I understand a word is two bytes , i create a two byte array

number var byte(2)

and i realize that a word is the same as a 16bit binary value ..

but im finding it hard to get my head around how i can duplicate the word type in sx/b

i basically need to store 16bit numbers in an eeprom

previously i did this using Number.highbyte , number.lowbyte etc

if anyone has any Sx/b maths routines i can study

also

in assembly if i wish to count a 16bit number im using the Addb command to add a bit using status.0 , the carry bit
im still a bit in the dark as to how this command actually works.. ive studied the code numerous times.. and im missing something

thanks again
·

Bean

SX/B will handle the values much easier if you make them "normal" BYTE variables.

numberL VAR BYTE
numberH VAR BYTE
working VAR BYTE

' add 8-bit to 16-bit
numberL=numberL + working
numberH = numberH + C

The addb command expands to:
SNB status.0
INC variable

Bean.

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·

Rsadeika

I guess I need some explanation about this subject also. In PBASIC you can declare a variable in the following manner - 'thing1 VAR Word', which I assume makes thing1 16 bits, I think a Word is 2 bytes = 16 bits. Now, I tried, in SX/B, 'thing1 var byte (2)', could this be another way of 'creating' a Word, or did I miss sometning in the correct usage of byte. I tried this method in some conversion code, with no success.

Bean

BYTE(2) will create an array, which is accessed differently than normal BYTE variables. Requring more code to do the calculations. If you want to do it that way, here is some code that will work:


DEVICE SX28, OSC4MHZ, TURBO, STACKX, OPTIONX
FREQ 4_000_000

number VAR BYTE(2) ' number(0) = LSB; number(1) = MSB
working VAR BYTE

Program Start

Start:
· PUT number,232,3 ' Store 1000 in number
· working=100

· ' Add "working" to "number"
· ASM
··· MOV __PARAM1,working
· · MOV FSR,#number
··· ADD IND,__PARAM1
· · INC FSR
··· ADDB IND,C
· · BANK $00
· ENDASM

END

Bean.

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Post Edited (Bean) : 3/28/2005 3:58:05 PM GMT

KenM

Below is a 16 bit add routine in pure assembly. The lower bytes are term0 and prod0.

You can put some initial values in term0 and prod0 and single step through the program watching what happens until you understand what is going on.

term0··· ds 1

prod0··· ds 1

term1··· ds 1

prod1··· ds 1

mov W, term0
add prod0, W

mov W, term1
snb C
movsz W, ++term1
add prod1, W

duffling

sorry i dont quite understand the line:
'PUT number,232,3 ' Store 1000 in number'

i may need some help with this .. everything else makes sense thou

Paul Baker

256*3+232=1000, understand now?

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duffling

whoops sorry i worked it out ! ......erk brain is at 4mhz today