fsr across memory banks

Javalin

Hi,

Im trying to use the FSR for indirect addressing across banks.· I believe the the FSR is in bank0 so should be accessible from where-ever.

When I debug the code the data is stored in the wrong locations in the banks.· If I try to put bank 2, or bank bank2 instructions in the code the compiler throws up "pass 2:· variable not in current bank" type messages.

What am I missing?

My code (snippits) is below:

org··$50····;bank 2 address on SX28
bank2··=·$
FIFO1Head· ····ds 1··················· ; FIFO head pointer
FIFO1Tail· ····ds 1··················· ; FIFO tail pointer
Temp1W··· ····ds 1··················· ; Temporary storage
Temp1R··· ····ds 1··················· ; Temporary storage
FIFO1Cnt ····ds 1··················· ; Current number of items the FIFO

org··$70····;bank 3 address on SX28

bank3··=·$
FIFO1·· ·= $················ ; 16 bytes for FIFO memory
·······ds 16····; this is for SERIAL1


then called from·the main program bank·:-

org·$200
;*********************************************************************************
; Function: ReadFIFO1
ReadFIFO1
·bank ·bank2
·test ·FIFO1Cnt··············· ; If FIFOCnt = 0, the
·snz·························· ·;· FIFO is "empty",
·· ·retp··················· ··;· no action
·mov· ·FsrSave, fsr·········· ; Save the FSR
·mov· ·w, #FIFO1·············· ; Indirectly address the FIFO-Puffer
·add· ·w, FIFO1Tail··············· ;· using the Head pointer
·mov· ·fsr, w················· ;
·mov· ·Temp1R, ind············ ; Read the value from the FIFO
·inc· ·FIFO1Tail·················· ; Set Tail to next location
·clrb ·FIFO1Tail.4················ ; If Tail = 16, "circle" around to 0
·dec· ·FIFO1Cnt··············· ; Decrement the item count
·mov· ·fsr, FsrSave··········· ; Restore the FSR
·mov· ·w, Temp1R·············· ; Copy the value to w
retp



Thanks

James

Bean

James, in your code:

mov fsr,w
mov Temp1R,ind ; This won't work because fsr is pointing to bank 3

you need to store ind in w then set fsr back to bank2 then copy from w to Temp1R.

remember BANK just sets FSR to the value, they are changing the same variable (FSR).


Try using w for temporary storage.
mov fsr,w
mov w,ind
bank bank2 ; DON'T DO "mov fsr,FsrSave" here·because it will destroy w
mov Temp1R,w
mov fsr,FsrSave ; I assume FsrSave is in the global area

Bean.

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Post Edited (Bean) : 3/16/2005 7:42:29 PM GMT

Paul Baker

I extracted the data stack functions from my forth interpretor, its not a fifo obviously, but it makes use of the fsr which works across all banks, maybe it can help you.

You may want to consider using the hidden FIFO in the SX since you get a 16 byte FIFO without using any of your memory banks.


Post Edited (Paul Baker) : 3/17/2005 3:33:11 AM GMT

Javalin

Hi Chaps,

Thanks for the answers.

James

pjv

Hi Paul;

Where did the 16 byte FIFO come from????

The "hidden" FIFO is only 8 bytes.......

Peter

Paul Baker

oops sorry was from my leaky memory