In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Peter Van der Zee wrote:

[quote="Peter Verkaik"]
You could do this
 

from location 1

mov m,#($+4)>>8

mov w,#adr1

call @mySub

adr1:   ;ret adr for this call

 

from location 2

mov m,#($+4)>>8

mov w,#adr2

call @mySub

adr2:   ;ret adr for this call

 

mySub:

;save m and w for reference or store to private stack or whatever

;do some code

retp  ;return to adr1 or adr2, specified by m and w

 

regards peter

 

Hi Peter;
While your suggestion is technically correct, I believe the your last line (retp ;return to adr1 or adr2, specified by m and w) may lead the reader to believe that the return is directed by the contents of M and W, rather than the entry at the top of the call stack.
The contents of M and W are totally irrelevant to return, you had simply chosen them as a convenient location to save the return address so that the subroutine code could use it if required.
Also, would loading M and W also not be written somewhat more simply as:
 
Location1      code                             ;arbitrary code
                   code                             ;arbitrary code
                   mov    m,#Return1>>8     ;get the upper 4 return address bits into m (must go through w for SX48/52)
                   mov    w,#Return1          ;get the lower 8 return address bits into w
                   call     Subroutine            ;go to the routine
Return1         code                             ;arbitrary code
                   code                             ;arbitrary code
 
Subroutine     code                             ;arbitrary code
                   code                             ;arbitrary code
                   retp
 
Cheers,
Peter (pjv)
[/quote][/quote]

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