Post by thread:[PIC]: 12c509 and SWAPF

oops, sorry about the tag. does swapf work on the w register? i.e., does swapf w,0 swap nibbles in w? Mark Skeels Engineer Competition Electronics spam_OUTmeskeelsTakeThisOuTearthlink.net Soli Deo Gloria! -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> swapf w,0 The first argument of swapf must be a file register. W is not a file register, so this does not work. The assembler will accept it, because w and f are just symbolic equivalents for the 0 and 1 that are used to specify the destination. Try "swapf f,0": it will be accepted by the assembler for the same reason that "swapf w,0" is accepted. Wouter van Ooijen van Ooijen Technische Informatica: http://www.xs4all.nl/~wf/ Jal compiler for PIC microcontrollers: http://www.xs4all.nl/~wf/wouter/jal -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

On Wed, 15 Aug 2001, wouter van ooijen & floortje hanneman wrote: > > swapf w,0 > > The first argument of swapf must be a file register. W is not a file > register, so this does not work. The assembler will accept it, because w and > f are just symbolic equivalents for the 0 and 1 that are used to specify the > destination. Try "swapf f,0": it will be accepted by the assembler for the > same reason that "swapf w,0" is accepted. Just to be clear, swapf w,0 is equivalent to: swapf INDF,W Since W and INDF are both equ'd to 0. If you want to swap the nibbles in W then you'll need to do something like this: movwf temp swapf temp,W (Unless you're using the 18cxx in which case you can write swapf wreg0,w ) If you want to shift W left 1 space then: movwf temp addwf temp,w ( a rlf will pick up the carry, but otherwise work just as well) Shift left 2: movwf temp addwf temp,f addwf temp,f addwf temp,w Or movwf temp rlf temp,f rlf temp,w andlw 0xfc ;Clear garbage shifted in Scott -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

----- Original Message ----- From: "wouter van ooijen & floortje hanneman" <.....wfKILLspam@spam@XS4ALL.NL> To: <PICLISTKILLspamMITVMA.MIT.EDU> Sent: Wednesday, August 15, 2001 3:33 PM Subject: Re: [PIC]: 12c509 and SWAPF snip.... > > swapf w,0 > > The first argument of swapf must be a file register. W is not a file end snip.... Looking at the memory map, I now see that w is not mapped to location 0 in RAM. However, Using my Clearwater Mathias emulator, the following instruction... incf w,0 appears to work, actually incrementing the w register. How come, if swapf doesnt'? So, incf works, swapf doesn't. Does this sound correct? Mark -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> does swapf work on the w register? No. ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, .....olinKILLspam.....embedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> Unless you're using the 18cxx in which case you can write > swapf wreg0,w WREG is also mapped to the register space on the 17xxx series. ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, EraseMEolinspam_OUTTakeThisOuTembedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> Using my Clearwater Mathias emulator, the following instruction... > > incf w,0 > > appears to work, actually incrementing the w register. > How come, if swapf doesnt'? It doesn't work, only appears to work in you case. The ",0" causes the result of the INCF to be written to W, which is why W gets modified. If W contains whatever FSR happens to be pointing to, then it will appear to increment. If you look into this more carefully you will see that it doesn't work. Of course you're messing with some third party emulator, so who knows what you will see. Try it with real MPLAB if you continue to have a problem. ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, olinspam_OUTembedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads