Hi Nishant

There is a register called the FSR (I think that stands for File Select
Register). You load the address of the start of the buffer into this
register. Then you read register 0 (I think it is called INDF) this
register will now hold the value of the register pointed to by the FSR.

Thus you would do something like this:

movlw   Buffer          ;this places the address of you 'Buffer' into w
movwf   FSR             ;place the address into FSR

Now you can work with the buffer:

movfw   INDF            ;This will put the value at Buffer into w

incf    FSR             ;Point to buffer+1

clrf    INDF            ;clear the data at Buffer+1

You can increment, decrement, add to & subtract from the FSR like with any
other register

I often use this method when I have a piece of code that performs a similar
function of a lot of registers.

Here is an example of how I define my variables:

        CBLOCK  0ch
        SaveW           ;01 holds W register durring interrupt
        SaveS           ;02 holds Status register durring interrupt
        SaveFSR         ;03 Holds copy of FSR durring interrupt
        T1              ;04 Timer values
        T2              ;05
        T3              ;06
        T4              ;07
        ENDC

I like using this method because if I want to add a variable say between
SaveS and SaveFSR (it makes more visual sense for whatever reason) the I
don't have to renumber all the variables. The compiler will renumber
consecutively them from 0ch until it reaches ENDC.

As for setting up the buffer, I have not had to do that so I couldn't tell
you for sure but I think you are right.

Cheers
        Dennis
____________________________________________________
FROST - Electronic Design, Manufacture & Consulting.
Dennis Frost
Tel:   +27 331 965125
Cel:   +83 2275216
Email: dennis.frost@pixie.co.za
Pietermaritzburg, South Africa
Products:       Medical Motivational equipment
                Timers for food processing
                Random number generator
                Temperature controllers
____________________________________________________

PS Anyone looking for someone in the hardware/software development fields,
I am available. I intend leaving South Africa for the West coast of the US
early this year.
----------

> From: Nishant Deshpande <nd4@DOC.IC.AC.UK>
> To: PICLIST@MITVMA.MIT.EDU
> Subject: programming question
> Date: 02 March 1997 09:57
>
> hi all,
>
> i've just started programming the pic - i've got the led's lit up
> etc etc now moving on to bigger & better things..
>
> a couple of questions regarding common practice :
>
> -       i started off assigning my own registers just using
>         CTR     EQU     20h
>         (for example)
>         what i meant was i wanted to use address 20h
>         now is it usual to use the 'DS' command to do this
>         kind of thing? i.e.
>                 ORG     20h
>         CTR     DS      1
>                 ORG     21h
>         CTR2    DS      1
>
>         i'm kinda unsure about the direct/indirect addressing..
>
> -       say i want a small buffer (i.e. maybe 12/16 bits) - i do this
>                 ORG     30h
>         BUFFER  DS      16
>
>         now how do i get at this buffer? i know i can do BUFFER+<offset>
>         but i want to use 'a variable' for the offset, increment it,
>         etc etc as i would in a high level language...
>
>         i thought of having another memory location holding a 'pointer'
>         to my buffer and then incrementing/decrementing this - but
>         trying to implement this seems kinda unnecessarily complex..
>
> any tips? i guess i'm still thinking high level language...
>
> thanks
>
> nishant
> ISE III BEng
> Incremental Sanity Erosion at Imperial College