Hi All,

Sorry to hassle with a seemingly simple problem. I'm trying to move onto
using MPLINK instead of absolute mode.

I am using 16F870. This chip has only shared GP ram. Only the SFR's are bank
fixed. Some of the general purpose ram is available in bank 0 and 2, and
some is available in bank 1 and 3. There is also a block that is available
in bank 0,1,2 and 3.

Here is the relevant part of 16f870.lkr:-

// GP-RAM available from banks 0 and 2
SHAREBANK   NAME=gprnobnk0     START=0x20     END=0x6F
SHAREBANK   NAME=gprnobnk0     START=0x120    END=0x16F

// GP-RAM available in banks 1 and 3
SHAREBANK   NAME=gprnobnk1     START=0xA0     END=0xBF
SHAREBANK   NAME=gprnobnk1     START=0x1A0    END=0x1BF

//GP-RAM available in all banks
SHAREBANK  NAME=gprnobnk2 START=0x70     END=0x7F
SHAREBANK  NAME=gprnobnk2 START=0xF0     END=0xFF
SHAREBANK  NAME=gprnobnk2 START=0x170    END=0x17F
SHAREBANK  NAME=gprnobnk2 START=0x1F0    END=0x1FF

So, when I want to reserve space for variables in my program, I have to use
UDATA_SHR.

What is confusing me though, is if I have the linker allocate a variable, I
do not know where it has put it, hence I don't know which bank to select to
access it. I know I can select the correct bank with "banksel", but surely
this means I have to do it every single time I access a variable?

Hard to explain what I mean. I'll make up some code now:

absolute mode:
cblock 0x20  ; 0x20 is bank 0
 temptime_l
 temptime_h
endc
...
org 0x04
inthanler:
        banksel INTCON ; INTCON is bank 0
        btfss           INTCON,RBIF
        retfie

        ; my made up code stores TMR1 value in temptime_l and temptime_h
upon RB0 interupt
        movw            TMR1H,W
        movwf           temptime_h
        movw            TMR1L,W
        movwf           temptime_l
        retfie


Ok, in that (made up) code, I only needed to banksel one time. Because I
knew that everything else was bank 0- all the SFR's and also my two temp
vars.

Now, if I use the linker and have it allocate a variable, I don't know which
bank it sits in. It might be in the block named gprnobnk2, in which case
bank selection isn't necessary. But if could put it in gprnobnk1 - which is
not accessible from bank 0. so, in absolute mode my code equivalent to the
above would need to be:-


UDATA_SHR
temptime_l      RES 1
temptime_h      RES 2

CODE

inthandler:
        banksel INTCON ; INTCON is bank 0
        btfss           INTCON,RBIF
        retfie

        ; my made up code stores TMR1 value in temptime_l and temptime_h
upon RB0 interupt
        movw            TMR1H,W
        banksel temptime_h      ; don't know where this is...
        movwf           temptime_h
        banksel TMR1L
        movw            TMR1L,W
        banksel temptime_l
        movwf           temptime_l
        retfie


So here I have gone from one to four banksel's in the same block of code.

I am being an idiot? Surely object/linker mode is not this fiddly and time
wasting?

Any tips appreciated,

thanks

jon

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