Post by thread:[PIC]: Memory Block Copy for PIC16F877

Hi everyone, For the 16F877 IC, the RAM space of bank0 from 0x70 to 0x7F can be accessed from any bank. I love this feature! Is there any way to expand it? If yes, would you please tell me how I can do it? If no, is there any way to copy the whole memory block or I have to do the following: movf x, w ; assume I am in bank 0 bank1 ; switch to bank 1 movwf y ; store it bank2 ; switch to bank 2 movwf z ; store it bank4 ; switch to bank 3 movwf zzz ; store it If I want to expand the mirror memory to another 16 locations, it seems like I have to write lots of code! Any there any faster and more efficent way? Thank a lot for all you help! thomas _________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. -- 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 04:28 PM 4/18/01 +0000, you wrote: >Hi everyone, > >For the 16F877 IC, the RAM space of bank0 from 0x70 to 0x7F can be accessed >from any bank. I love this feature! > >Is there any way to expand it? If yes, would you please tell me how I can do >it? In the AVR, the entire ram space is accessible from any bank. In fact there are no banks. :) In the Pic, you get what you get. There's no way to "expand" that. -- Dave's Engineering Page: http://www.dvanhorn.org Where's dave? http://www.findu.com/cgi-bin/find.cgi?kc6ete-9 -- 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

>If I want to expand the mirror memory to another 16 locations, it seems like >I have to write lots of code! Any there any faster and more efficent way? use the indirect addressing registers to access either the source or destination, which ever is in the other bank to the one you are currently in. If done correctly you may not even need to copy the registers between banks. -- 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

>If no, is there any way to copy the whole memory block or I have to do the >following: > > movf x, w ; assume I am in bank 0 > > bank1 ; switch to bank 1 > movwf y ; store it > > bank2 ; switch to bank 2 > movwf z ; store it > > bank4 ; switch to bank 3 > movwf zzz ; store it No, there's no way to expand the memory range. However, you can just use the FSR to transfer data across memory banks. A simple way is to set up your variables so that they are in consecutive address locations. cblock 0x20 x y z zzz endc movlw y movwf FSR ; load FSR with first storage address movf x, W ; load data to store movwf INDF ; store in y incf FSR, F movwf INDF ; store in z incf FSR, F movwf INDF ; store in zzz This might be a few instructions better than your initial method, as your bank switching probably requires two instructions (I don't know what your macros look like) while 'incf FSR, F' always takes one instruction. If you want to copy a larger block of memory values, you can always just put the "incf, FSR" and "movwf INDF" into a loop and check for the last address to overflow. I'm not sure, but I think most of the datasheets for PICs that have EEPROM memory will show you an example of this sort of thing. --Andrew _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com -- 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

Thank you! I will try this and see what happens. Thomas {Quote hidden}>From: Drew Vassallo <spam_OUTsnurpleTakeThisOuTHOTMAIL.COM> >Reply-To: pic microcontroller discussion list <.....PICLISTKILLspam@spam@MITVMA.MIT.EDU> >To: PICLISTKILLspamMITVMA.MIT.EDU >Subject: Re: [PIC]: Memory Block Copy for PIC16F877 >Date: Wed, 18 Apr 2001 13:03:17 -0400 > >>If no, is there any way to copy the whole memory block or I have to do the >>following: >> >> movf x, w ; assume I am in bank 0 >> >> bank1 ; switch to bank 1 >> movwf y ; store it >> >> bank2 ; switch to bank 2 >> movwf z ; store it >> >> bank4 ; switch to bank 3 >> movwf zzz ; store it > >No, there's no way to expand the memory range. However, you can just use >the FSR to transfer data across memory banks. A simple way is to set up >your variables so that they are in consecutive address locations. >cblock 0x20 >x >y >z >zzz >endc > >movlw y >movwf FSR ; load FSR with first storage address >movf x, W ; load data to store >movwf INDF ; store in y >incf FSR, F >movwf INDF ; store in z >incf FSR, F >movwf INDF ; store in zzz > > >This might be a few instructions better than your initial method, as your >bank switching probably requires two instructions (I don't know what your >macros look like) while 'incf FSR, F' always takes one instruction. If you >want to copy a larger block of memory values, you can always just put the >"incf, FSR" and "movwf INDF" into a loop and check for the last address to >overflow. > >I'm not sure, but I think most of the datasheets for PICs that have EEPROM >memory will show you an example of this sort of thing. > >--Andrew >_________________________________________________________________ >Get your FREE download of MSN Explorer at http://explorer.msn.com > >-- >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 > > _________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. -- 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

> Careful if you use ICD. These are also used by the debugger. > Very funny things happens if you write to it. > > Quentin Write to what? The FSR? I do that all the time when debugging on ICD. Bob Ammerman RAm Systems (contract development of high performance, high function, low-level software) -- 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

> For the 16F877 IC, the RAM space of bank0 from 0x70 to 0x7F can be accessed > from any bank. I love this feature! I like it too. I use it mostly for "general purpose registers". > Is there any way to expand it? No. It is what it is. Note that some PICs don't have this at all. The 18 family has a different approach where you can have 128 common bytes in an "access bank". > If I want to expand the mirror memory to another 16 locations, it seems like > I have to write lots of code! That would be rather silly in most circumstances. > Any there any faster and more efficent way? Use an 18 family PIC or design the software structure to fit what you have instead of trying to change the hardware into something it isn't. ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, .....olinKILLspam.....embedinc.com, http://www.embedinc.com -- 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