Post by thread:[PIC]: 12C509 Call Limitation

Hello all - I've recently began tackling the 12C509 and quickly discovered the limitation of using a Call outside of the first 256 "bytes" of each 512 page. I've looked around and found information on related workarounds centered on the 16CXX line using the PCLATH register, which the 12CXXX does not have. Can someone point me in the right direction? Thanks Mike Evans -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Evans Michael E Maj ACC/XPPI wrote: > > Hello all - > > I've recently began tackling the 12C509 and quickly discovered the > limitation of using a Call outside of the first 256 "bytes" of each 512 > page. I've looked around and found information on related workarounds > centered on the 16CXX line using the PCLATH register, which the 12CXXX does > not have. Can someone point me in the right direction? Hi Mike, the hardware will only call the first 256 words as it leaves PC bit 8 cleared. I don't know of any way of getting around this hardware fact. The best solution is to call the function which is on the first block (it has to be there), then simply with one program word just goto the second 256 block where the actual "guts" of the function is. The return will work fine. Messy but lets you use the whole memory for fucntions. :o) -Roman -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Thanks Roman - I'll play with the hardware later..but this is how I understand it...All calls and returns must be placed in the 1st 256 "bytes" of the 512 code space but a return may be in the upper 256 because the PC will map back to page 1 (1st 256). i.e. __________________ page 1 (1st 256) ... call xyz ... xyz goto xyz_code page 1 (2nd 256) xyz_code .. .. return __________________ Mike _\\|//_ (` o-o ') ____________O-(_)-O______________ ________.oooO_____Oooo.__________ ( ) ( ) \ ( ) / \_) (_/ {Original Message removed}

Actually the returns are fine. The chips have a full functional 12-bit hardware stack. Although only 2 levels of course. So as long as the START ADDRESS of the function you call is on block 0, the end address of the function (and any gotos it has) can be anywhere within the first 512 page. Page 19 of the datasheet shows it pretty clearly, the only problem is the CALL which always has bit 8 clear. Returns are faithful. :o) -Roman Evans Michael E Maj ACC/XPPI wrote: > > Thanks Roman - > I'll play with the hardware later..but this is how I understand it...All > calls and returns must be placed in the 1st 256 "bytes" of the 512 code > space but a return may be in the upper 256 because the PC will map back to > page 1 (1st 256). i.e. > > {Original Message removed}

Got it...not too messy. Thanks again -- Mike _____________ Roman Black Wrote: Actually the returns are fine. The chips have a full functional 12-bit hardware stack. Although only 2 levels of course. So as long as the START ADDRESS of the function you call is on block 0, the end address of the function (and any gotos it has) can be anywhere within the first 512 page. Page 19 of the datasheet shows it pretty clearly, the only problem is the CALL which always has bit 8 clear. Returns are faithful. :o) -Roman Evans Michael E Maj ACC/XPPI wrote: {Quote hidden}> > Thanks Roman - > I'll play with the hardware later..but this is how I understand it...All > calls and returns must be placed in the 1st 256 "bytes" of the 512 code > space but a return may be in the upper 256 because the PC will map back to > page 1 (1st 256). i.e. > > Evans Michael E Maj ACC/XPPI wrote: > > > > Hello all - > > > > I've recently began tackling the 12C509 and quickly discovered the > > limitation of using a Call outside of the first 256 "bytes" of each 512 > > page. I've looked around and found information on related workarounds > > centered on the 16CXX line using the PCLATH register, which the 12CXXX > does > > not have. Can someone point me in the right direction? > > Hi Mike, the hardware will only call the first 256 words > as it leaves PC bit 8 cleared. I don't know of any way > of getting around this hardware fact. > > The best solution is to call the function which is on > the first block (it has to be there), then simply with > one program word just goto the second 256 block where > the actual "guts" of the function is. The return will > work fine. > > Messy but lets you use the whole memory for fucntions. >:o) > -Roman > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> I've recently began tackling the 12C509 and quickly discovered the > limitation of using a Call outside of the first 256 "bytes" of each 512 > page. I've looked around and found information on related workarounds > centered on the 16CXX line using the PCLATH register, which the 12CXXX does > not have. Can someone point me in the right direction? Not without know what you are trying to accomplish. Are you asking how to convert the code to a 16Cxx or how to deal with the 12C509 limitation? ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, spam_OUTolinTakeThisOuTembedinc.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

I'm looking to handle the 12CXXX call limitation...I believe (Roman Black) has pointed me in the right direction. I've attached the tread below your response. Any other approach is welcome. Thanks -- Mike {Original Message removed}

The short answer is that you make subroutine stubs that GOTO somewhere else where the subroutine body is located (including higher in that page beyond 0x100). The limitation is on CALL not on RETLW so it's ok to RETLW from there. For example: Subr1: ; some code here retlw 0 becomes: Subr1: goto Subr1_h ;... more code here org 0x110 ; f.ex. Subr1_h: ; ... code here retlw 0 You may have to operate the paging bits (PCLATH) and save them first before going 'high'. I just did something like this so it was fresh ;-) Peter -- 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

"Peter L. Peres" wrote: > You may have to operate the paging bits (PCLATH) and save them first > before going 'high'. > > I just did something like this so it was fresh ;-) No PCLATH in the 509. Use STATUS,PA0 I only know that offhand because I was just playing with it. ;-) -- Best regards Tony mICros http://www.bubblesoftonline.com .....salesKILLspam@spam@bubblesoftonline.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

Tony Nixon wrote: > No PCLATH in the 509. Use STATUS,PA0 Right, that's what I meant ;-) Peter -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

>Not without know what you are trying to accomplish. Are you asking how to >convert the code to a 16Cxx or how to deal with the 12C509 limitation? I'd love to see a "howto" convert 16F84 to 12C508/9 guide. Telling all the pros and cons, and the pitfalls Call me lazy, but sometimes I'm a complete dumb :o) -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

If you're talking about code translation between the two processors, my PIC Microcontroller Instruction Set Comparison Matrix (at epicis.piclist.com) can help. It won't help you will differences between the two chip's peripherial sets, but it will show what instructions are available (by core type) and the status flags affected by each instruction. Douglas Wood Software Engineer dbwoodKILLspamkc.rr.com Home of the EPICIS Development System for the PIC and SX http://epicis.piclist.com {Original Message removed}

>If you're talking about code translation between the two processors, my PIC >Microcontroller Instruction Set Comparison Matrix (at epicis.piclist.com) >can help. It won't help you will differences between the two chip's >peripherial sets, but it will show what instructions are available (by core >type) and the status flags affected by each instruction. Of course it can, and helps a lot, I'm reformating it to be PDF-able in only one sheet... -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

I'm working on updating it to include more information. Also, there will links from each instruction to an expanded page for each instruction... Douglas Wood Software Engineer .....dbwoodKILLspam.....kc.rr.com Home of the EPICIS Development System for the PIC and SX http://epicis.piclist.com {Original Message removed}

At 08:43 PM 5/24/01 -0300, Alexandre Domingos F. Souza wrote: > >Not without know what you are trying to accomplish. Are you asking how to > >convert the code to a 16Cxx or how to deal with the 12C509 limitation? > > I'd love to see a "howto" convert 16F84 to 12C508/9 guide. > Telling all the pros and cons, and the pitfalls Check out "Quozl's 16F84 to 12C509 Porting Checklist" at http://quozl.netrek.org/porting-16f84-12c509/ Hope this helps. dwayne Dwayne Reid <EraseMEdwaynerspam_OUTTakeThisOuTplanet.eon.net> Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 17 years of Engineering Innovation (1984 - 2001) * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

Alexandre Domingos F. Souza wrote: > > >Not without know what you are trying to accomplish. Are you asking how to > >convert the code to a 16Cxx or how to deal with the 12C509 limitation? > > I'd love to see a "howto" convert 16F84 to 12C508/9 guide. Telling all the pros and cons, and the pitfalls Hi Alexandre, I have been using a suggestion that someone here gave me a couple of months ago. Don't think "convert" think about making the code from the start that works with both PICs. This lets you develop the project on the easy F84 then just change the "development mode" in MPLAB and re-compile and it is ready for the other PIC. Here are a few bits from my code: ;============================================================================== ; processor defined... ; NOTE!! all I have to do is change the processor type in ; MPLAB/option/development mode/, and it is all automatic now. ; I do not have to edit this file at all to change processor type. IFDEF __16C505 include <p16C505.inc> ELSE ; for 16F84A include <p16F84A.inc> ; which version to compile ENDIF ;============================================================================== ;ERRORLEVEL -224 ; suppress annoying message because of option/tris ;ERRORLEVEL -302 ; suppress message because of bank select in setup ports LIST b=5, n=97, t=ON, st=OFF ; ; absolute listing tabs=5, lines=97, trim long lines=ON, symbol table=OFF IFDEF __16C505 __CONFIG _MCLRE_OFF & _CP_OFF & _WDT_OFF & _IntRC_OSC_RB4EN ELSE ; for 16F84A __CONFIG _CP_OFF & _WDT_OFF & _PWRTE_ON & _XT_OSC ENDIF ;============================================================================== ; Variables here ;------------------------------------------------- IFDEF __16C505 #define RAM_START 0x08 #define RAM_END RAM_START+23 ; is the last reg ELSE ; for 16F84A #define RAM_START 0x0C #define RAM_END RAM_START+67 ; is the last reg ENDIF ;------------------------------------------------- CBLOCK RAM_START temp ; for use by any function latch ; used for my bit flags delay_hi ; for general delay loops delay_lo ; flash_count ; dec, each fake int (30.5Hz) flash_bit_count ; to sequence which bit to flash flash_data ; the byte to flash on the led ; these 3 are only used at startup. ;-------------------- timer_hi ; main timer (hi byte of timer0) ENDC ;------------------------------------------------- ;============================================================================== ; defines and stuff here ;------------------------------ ; specific pin stuff IFDEF __16C505 #define INPUT PORTC,0 ; the input pin #define OUTPUT PORTB,5 ; the output pin #define LED PORTB,4 ; the led pin ELSE ; 16F84 #define INPUT PORTA,1 ; the input pin #define OUTPUT PORTA,0 ; the output pin #define LED PORTA,3 ; the led pin ENDIF ;------------------------------ ; custom instructions here #define skpwne skpnz ; after subxx, uses zero #define skpweq skpz ; after subxx, uses zero #define skpwle skpc ; after subxx, uses carry #define skpwgt skpnc ; after subxx, uses carry ;============================================================================== ;****************************************************************************** ; SETUP runs this only once, must be run before entering main ;****************************************************************************** ; NOTE!! we do reg initialising and also startup stuff like read dipsw ;------------------ setup ; goto tag ;------------------ ;------------------------------------------------- ; set up OPTION IFDEF __16C505 ;------------------------- movlw b'10000011' ; ; x------- ; 7, 1=dis, wake up on pin change ; -x------ ; 6, 0=en, portb weak pullups ; --x----- ; 5, timer0 source, 0=internal clock ; ---x---- ; 4, timer0 ext edge, 1=\ ; ----x--- ; 3, prescaler assign, 1=wdt, 0=timer0 ; -----x-- ; 2,1,0, prescaler rate select ; ------x- ; 011=16 timer0 ; -------x ; option ; load data into OPTION_REG ;------------------------- ELSE ; 16F84 ;------------------------- movlw b'00000011' ; ; x------- ; 7, 0=en, portb pullups ; -x------ ; 6, 1=/, int edge select bit ; --x----- ; 5, timer0 source, 0=internal clock ; ---x---- ; 4, timer0 ext edge, 1=\ ; ----x--- ; 3, prescaler assign, 1=wdt, 0=timer0 ; -----x-- ; 2,1,0, prescaler rate select ; ------x- ; 011=16 timer0 ; -------x ; banksel OPTION_REG ; go reg bank 1 movwf OPTION_REG ; load data into OPTION_REG banksel 0 ; back to normal bank 0 ;------------------------- ENDIF ;------------------------------------------------- ; other setup code here ;------------------------------------------------- goto main_after_setup ; return to main ;****************************************************************************** Hope that helps. Remember to not use SUBLW or ADDLW, obviously no interrupts, and try to keep most things sequential so you can use gotos instead of calls. :o) -Roman -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email @spam@listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

>Hi Alexandre, I have been using a suggestion that >someone here gave me a couple of months ago. >Don't think "convert" think about making the code >from the start that works with both PICs. This lets you >develop the project on the easy F84 then just change >the "development mode" in MPLAB and re-compile and >it is ready for the other PIC. Hi Roman, always helpful :o) The problem is that I NEVER SEEN A PIC 12C508 :o) I had neither a clue of how different it was from 16F84. When I get my JWs, I'll play with them to learn, and so I think I'll be able to use the "dual mode" code hehehe BTW, The timer project is completed in the 16F84. Now it's just a time of converting it to 12C508. It's working right now here on the protoboard :o) Nice birthday gift, hehehe :oD -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email KILLspamlistservKILLspammitvma.mit.edu with SET PICList DIGEST in the body