transfer a string from ROM to an array

[HenrikOlsson]

Hi,
Looking at the DT-INTS_18 file Darrel is declaring variables for saving the FSR's:

fsave0H     var WORD  BANK0  SYSTEM   ' locations for FSR registers
fsave1H     var WORD  BANK0  SYSTEM
fsave2H     var WORD  BANK0  SYSTEM
fsave0L     var WORD  BANK0  SYSTEM   ' low priority FSR locations
fsave1L     var WORD  BANK0  SYSTEM
fsave2L     var WORD  BANK0  SYSTEM

There's also a section towards the end that says

; ---[See if we need to save TBLPTR]------------------------------------------

Which sets a flag SAVE_TBLPTR = 1 when any PBP command that uses TBLPTR is used and in the ReEnterPBP-18 file he's declaring variables for TBLPTR like:

    TBLPTRU_H     VAR HP_Vars[31]
      TBLPTRU_SaveH VAR TBLPTRU_H.lowbyte
    TBLPTR_H      VAR HP_Vars[32]
      TBLPTRH_SaveH VAR TBLPTR_H.highbyte
      TBLPTRL_SaveH VAR TBLPTR_H.lowbyte

And then, further down in that file:

@ if Save_TBLPTR == 1
    TBLPTRU_SaveH = TBLPTRU
    TBLPTRH_SaveH = TBLPTRH
    TBLPTRL_SaveH = TBLPTRL
@ endif

So, to me, it looks like DT-INTS is handling all that stuff and you would/should only need to worry about it of you're using the FSR's or TBLPTR in any other ASM routines which would mean that DT-INTS does't detect them being used and therefor doesn't save them.

Of course I may have it all wrong in which case I hope someone who can understand the ASM in DT-Ints better then me can explain what's going on.

/Henrik.

[richard]

thanks for that henrik I never thought to look at how dt ints works . dt's code leaves nothing to chance ,I'm left humbled again

[Marcick]

Guys,
about Darrel code I could put my hand on fire.
about my code I can bet there are bugs ...
but with your help now I have everything clear and know where problems can be or not. I have DTint and other ISR where I'll take care about FSR and TBLPTR.
so, many thanks again for your support !
bye
Marco

[Marcick]

Hi Richard,
maybe I'm doing some confusion and about to say something of funny, but I have a doubt:
How do you ensure in this code that you are in the correct bank reading the address of "buffer" ?

ASM
Flash2Ram macro buffer, msg ; Fills the buffer from flash msg
   movlw   UPPER msg
   movwf   TBLPTRU
   movlw   HIGH msg
   movwf   TBLPTRH
   movlw   LOW msg
   movwf   TBLPTRL
   movlw   low buffer		
   movwf   FSR2L
   movlw   High buffer
   movwf   FSR2H
   L?CALL  _bfill
   endm
ENDASM

[richard]

buffer does not actually exist its just a label in the macro , when assembled
@ Flash2Ram _buff , _String1 , produces

000168 0E00               M    movlw   UPPER _String1
0016A 6EF8                 M    movwf   TBLPTRU
00016C 0E01               M    movlw   HIGH _String1
00016A 6EF8               M    movwf   TBLPTRU
00016C 0E01               M    movlw   HIGH _String1
00016E 6EF7               M    movwf   TBLPTRH
000170 0E3E               M    movlw   LOW _String1
000172 6EF6               M    movwf   TBLPTRL
000174 0E1A               M    movlw   low _buff            
000176 6ED9               M    movwf   FSR2L
000178 0E00               M    movlw   High _buff
00017A 6EDA               M    movwf   FSR2H
                          M    L?CALL  _bfill

the label "buffer" is replaced with the symbol of the intended target
at no stage do we actually write directly to the "buffer" we simply load its address (from the symbol table) into the fsr regs
the bfill subroutine then fills the "buffer" indirectly via the fsr regs
macro's are not subroutines they are just another shortcut way to save typing, every time the macro is encountered the real code as above is inserted into your program

[Marcick]

Yes, but while _String1 is a fixed address that point to a univoque ROM location, isn't _buff a RAM location that points to different register according to the current bank ?
Marco

[richard]

evidently I'm not explaining it well
we never write directly to _buff we do it 'indirectly' via the 16 bit full address in fsr2 its called INDIRECT ADDRESSING read the chapter in the data sheet ,(this is how pic18's have arrays that can be bigger than a ram bank)
bank select is not applicable to indirect addressing