Post by thread:[PIC]: W Register

Hi Guys, Another simple question (I am sure) from a Newbie, but I have searched and can not find an answer anywhere. Probably scanned passed it a dozen times, I am sure! If I use any byte instruction and place the result back into the file, is my W register cleared or does it maintain it's original value for further use? Example; MOVF GPIO, W ; Read Port ANDLW B'00000111' ; Mask out unwanted bits & store in W IORWF TEST1, F ; Store result original TEST1 file AND masked GPIO MOVF CHECK ; Store masked version of GPIO Can this be done? Regards, Sean -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

It keeps it origenal value. >>> spam_OUTsdalcornTakeThisOuTAVION.COM.AU 01/14/02 02:48PM >>> Hi Guys, Another simple question (I am sure) from a Newbie, but I have searched and can not find an answer anywhere. Probably scanned passed it a dozen times, I am sure! If I use any byte instruction and place the result back into the file, is my W register cleared or does it maintain it's original value for further use? Example; MOVF GPIO, W ; Read Port ANDLW B'00000111' ; Mask out unwanted bits & store in W IORWF TEST1, F ; Store result original TEST1 file AND masked GPIO MOVF CHECK ; Store masked version of GPIO Can this be done? Regards, Sean -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

At 03:18 PM 14/01/2002 +1100, you wrote: >Hi Guys, > >Another simple question (I am sure) from a Newbie, but I have searched and >can not find an answer anywhere. Probably scanned passed it a dozen times, I >am sure! > >If I use any byte instruction and place the result back into the file, is my >W register cleared or does it maintain it's original value for further use? It is not affected - it still have the old value. >Example; > >MOVF GPIO, W ; Read Port >ANDLW B'00000111' ; Mask out unwanted bits & store in W >IORWF TEST1, F ; Store result original TEST1 file AND masked GPIO >MOVF CHECK ; Store masked version of GPIO Do you mean MOVWF for the last instruction? If so, then yes. For better readability I'd probably do the IORWF last though. The MOVWF doesn't actually 'move' the byte - just copies it to the specified register. W reg still contains the byte as well. Regards... -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Hi David and Peter, Thanks for your responses to my silly question. >> MOVF CHECK ; Store masked version of GPIO > > Do you mean MOVWF for the last instruction? If so, then yes. Yes. I did, sorry. > For better readability I'd probably do the IORWF last though. OK, Thanks. > The MOVWF doesn't actually 'move' the byte - just copies it > to the specified register. W reg still contains the byte as well. Yes, I had assumed as much, but could not actually find it in black and white. Thought it best to check with the list gurus rather than assume. Still waiting for "PIC Programming for Dummies" to be published. :-) Thanks again, Sean -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Hello Sean & PIC.ers, w won't be changed, but for the future be advised that the much-under-rated MPSIM part of MPLAB is extremely useful for answering these queries. This *really* starts to matter when you get to 16bit manipulation, arithmetic & the like. Just write a very small stretch of code, including your target sequence. Load the watch window with relevant fregisters, compile..run..edit initial conditions..compile..run..edit etc, etc, This might not seem very scientific, but can rescue your sanity. {Quote hidden}>Date: Mon, 14 Jan 2002 15:18:34 +1100 >From: Sean Alcorn - Avion Sydney <.....sdalcornKILLspam@spam@AVION.COM.AU> >Subject: [PIC]: W Register > >Hi Guys, > >Another simple question (I am sure) from a Newbie, but I have searched and >can not find an answer anywhere. Probably scanned passed it a dozen times, I >am sure! > >If I use any byte instruction and place the result back into the file, is my {Quote hidden}>W register cleared or does it maintain it's original value for further use? > >Example; > >MOVF GPIO, W ; Read Port >ANDLW B'00000111' ; Mask out unwanted bits & store in W >IORWF TEST1, F ; Store result original TEST1 file AND masked GPIO >MOVF CHECK ; Store masked version of GPIO > >Can this be done? > >Regards, > >Sean > bestos, John e-mail from the desk of John Sanderson, JS Controls. Snailmail: PO Box 1887, Boksburg 1460, Rep. of South Africa. Tel/fax: Johannesburg 893 4154 Cellphone no: 082 741 6275 email: jsandKILLspampixie.co.za Manufacturer & purveyor of laboratory force testing apparatus, and related products and services. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.