Post by thread:[PIC]: PCLATH Bug in MPLAB-SIM ?

Hi everyone! Currently i try to write a little training program to learn more about jumping between page boundaries. (inspirated by a Msg from Olin who do this with linker sections ...) But when i try my code in MPLAB-SIM the jumps/calls between the pages work fine just the return dosn't work like documented in the PIC-Datasheets. The problem seems to be that MPLAB-SIM dosn't restore the PCLATH (from the stack). Is this a known Bug in MPLAB-SIM or do i something wrong? TIA Christian -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

Christian Dorner <.....docKILLspam@spam@AUSTROSOL.COM> writes: > But when i try my code in MPLAB-SIM the jumps/calls between the pages work > fine just the return dosn't work like documented in the PIC-Datasheets. The > problem seems to be that MPLAB-SIM dosn't restore the PCLATH (from the > stack). > > Is this a known Bug in MPLAB-SIM or do i something wrong? Where in the data sheet do you find any claim that doing a return modifies PCLATH? On the parts that I've worked with, return has no effect on PCLATH. I usually wind up with something like: ; in first 2KW region: ... movlw r2sub>>8 movwf pclath call r2sub clrf pclath ; restore PCLATH to point to page 0 ... call r0sub ... r0sub: ... return ... ; in second 2KW region: org 0800h ... r2sub: ... return -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

> Where in the data sheet do you find any claim that doing a return modifies > PCLATH? > > On the parts that I've worked with, return has no effect on PCLATH. > I usually wind up with something like: Thanks for the fast answer but i've found the problem. (You also descriped above). I don't read the datasheet careful enought. (might be a problem of my bad english, too) I've fixed it with a small macro which checks the program location (page) where it inserted and "restores" (set it with the right values) the PCLATH. If anyone cares about, there it is: ---- snip ----------------------------------------------- poppclath macro if $ >= 0x0000 & $ <= 0x07ff bcf PCLATH,3 ; Set PCLATH to Page 0 bcf PCLATH,4 endif if $ >=0x0800 & $ <= 0x0fff bsf PCLATH,3 ; Set PCLATH to Page 1 bcf PCLATH,4 endif if $ >=0x1000 & $ <= 0x17ff bcf PCLATH,3 ; Set PCLATH to Page 2 bsf PCLATH,4 endif if $ >=0x1800 & $ <= 0x1fff bsf PCLATH,3 ; Set PCLATH to Page 3 bsf PCLATH,4 endif endm ---- snip ----------------------------------------------- After a CALL i insert this "POPPCLATH" to fix the PCLATH. cu, Christian -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam.....mitvma.mit.edu with SET PICList DIGEST in the body

Christian Dorner wrote: {Quote hidden}> > Hi everyone! > > Currently i try to write a little training program to learn more about > jumping between page boundaries. (inspirated by a Msg from Olin who do this > with linker sections ...) > > But when i try my code in MPLAB-SIM the jumps/calls between the pages work > fine just the return dosn't work like documented in the PIC-Datasheets. The > problem seems to be that MPLAB-SIM dosn't restore the PCLATH (from the > stack). > > Is this a known Bug in MPLAB-SIM or do i something wrong? > > TIA > > Christian > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email EraseMElistservspam_OUTTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body MPLAB or the processor does not restore the PCLATH after a CALL or GOTO instruction. Here is a little snippet I use to demonstrate ROM addressing. This one will not work because the PCLATH register is not set for the call... Title "mICros PCLATH Program 2" list p=16f873 ; processor type ; ; The purpose of this program is to demonstrate the PCLATH register ; jumping over a page boundary ; PCLATH equ 0x0A ; define PCLATH register ; ; ------------- ; PROGRAM START ; ------------- ; org 0000h ; code starts at address 0 Loop call Delay ; execute Delay subroutine goto Loop ; repeat forever nop nop Error1 goto Error1 ; ; Delay subroutine starts at 0800h ; org 0800h Error2 goto Error2 nop nop nop Delay nop ; very small delay subroutine nop return end This one will not work either because the PCLATH is not restored after the call... Title "mICros PCLATH Program 3" list p=16f873 ; processor type ; ; The purpose of this program is to demonstrate the PCLATH register ; jumping over a page boundary ; PCLATH equ 0x0A ; define PCLATH register ; ; ------------- ; PROGRAM START ; ------------- ; org 0000h ; code starts at address 0 Loop movlw High(Delay) movwf PCLATH call Delay ; execute Delay subroutine goto Loop ; repeat forever nop nop Error1 goto Error1 ; ; Delay subroutine starts at 0800h ; org 0800h Error2 goto Error2 nop nop nop Delay nop ; very small delay subroutine nop return end This one will work because PCLATH was set before the call and restored after the call... Title "mICros PCLATH Program 4" list p=16f873 ; processor type ; ; The purpose of this program is to demonstrate the PCLATH register ; jumping over a page boundary ; PCLATH equ 0x0A ; define PCLATH register ; ; ------------- ; PROGRAM START ; ------------- ; org 0000h ; code starts at address 0 Loop movlw High(Delay) movwf PCLATH call Delay ; execute Delay subroutine clrf PCLATH goto Loop ; repeat forever nop nop Error1 goto Error1 ; ; Delay subroutine starts at 0800h ; org 0800h Error2 goto Error2 nop nop nop Delay nop ; very small delay subroutine nop return end There is a more detailed explanation in the project file at... http://www.bubblesoftonline.com/projects.zip -- Best regards Tony mICros http://www.bubblesoftonline.com salesspam_OUTbubblesoftonline.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email @spam@listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

> Currently i try to write a little training program to learn more about > jumping between page boundaries. (inspirated by a Msg from Olin who do this > with linker sections ...) > > But when i try my code in MPLAB-SIM the jumps/calls between the pages work > fine just the return dosn't work like documented in the PIC-Datasheets. The > problem seems to be that MPLAB-SIM dosn't restore the PCLATH (from the > stack). That's because the PIC doesn't restore PCLATH on a return. You have to manually "restore" it to the current page after the return from a call. Yes, I think this sucks too. Take a look at my GCALL (Global CALL) macro in STD.INS.ASPIC at http://www.embedinc.com/pic. It sets PCLATH to the target, does the CALL, then sets PCLATH back to the current page after the return. ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, KILLspamolinKILLspamembedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

> I've fixed it with a small macro which checks the program location (page) > where it inserted and "restores" (set it with the right values) the PCLATH. There is a pseudo-op called PAGESEL that does this. The advantage of PAGESEL is that it works with the linker so that you don't need to know what page you're on at assembly time. Please fix your reply address so that the default is to the list instead of you. I'm getting tired of fixing it manually every time. ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, spamBeGoneolinspamBeGoneembedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: To leave the PICList TakeThisOuTpiclist-unsubscribe-requestEraseMEspam_OUTmitvma.mit.edu

> > Please fix your reply address so that the default is to the list instead > of > > you. I'm getting tired of fixing it manually every time. > > Done. No, you still have REPLY: set to you. I had to manually edit the TO: address of this reply to make it go to the list. Yes, I know the PIClist server should do this automatically, but unfortunately it doesn't. ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, olinEraseME.....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

> No, you still have REPLY: set to you. I had to manually edit the TO: > address of this reply to make it go to the list. Yes, I know the PIClist > server should do this automatically, but unfortunately it doesn't. Olin, in this case you're wrong. Check out the msg header, the REPLY-TO header entry is set to PICLIST ... the only thing is that my name appears in the TO line in your mail program. (But this does not affect the function of the reply) I've configurated now my mail-server to change this, too. I hope now for the future everything in my mails will be right. (Except for the content of the msg, i can't guarantee to ask further stupid questions, but i'll do my best to avoid this :-) cu, Christian -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads