Post by thread:[PIC]: OSCCAL, 12CE674 and HiTech C

Hi all, I've checked the PIC Faq on this subject and found some messages, but none of them were of much help. I try to get the preprogrammed calibration code in OSCCAL. To do this I first put "OSCCAL=_READ_OSCCAL_DATA();", and then tried without it. In both cases, the code generated by the compiler (PICC)is the same: The startup code is: 0000 0183 poweru clrf 0x3 0001 3000 movlw 0x0 0002 008A movwf 0xA 0003 2804 goto intlevel0 and the last program memory word gets like this: 07FF 2804 goto intlevel0 This, of course, will not work at all. How must I do? Thanks, Howard. _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

> I try to get the preprogrammed calibration code in OSCCAL. To do this I > first put "OSCCAL=_READ_OSCCAL_DATA();", and then tried without it. In both > cases, the code generated by the compiler (PICC)is the same: > > The startup code is: > > 0000 0183 poweru clrf 0x3 > 0001 3000 movlw 0x0 > 0002 008A movwf 0xA > 0003 2804 goto intlevel0 > > and the last program memory word gets like this: > > 07FF 2804 goto intlevel0 > > This, of course, will not work at all. How must I do? Fresh from the factory, the last word in program memory is set to a MOVLW with the recommended OSCCAL value. At reset, execution start there, then wraps to 0 on the next instruction. To use the calibration value you must somehow save or use the value in W before stomping on it. You must also not program over the last word in memory or bulk erase the device if it is erasable. The code above does a MOVLW 0, which looses the value. ******************************************************************** Olin Lathrop, embedded systems consultant in Littleton Massachusetts (978) 742-9014, .....olinKILLspam@spam@embedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestKILLspammitvma.mit.edu

At 06:28 PM 6/14/01 -0400, Olin Lathrop wrote: >Fresh from the factory, the last word in program memory is set to a MOVLW >with the recommended OSCCAL value. At reset, execution start there, then >wraps to 0 on the next instruction. Actually, the above is accurate for the 12 bit core devices. The 12CE674 is a 14 bit core, so the last word of memory is encoded as a RETLW 0xNN instead of MOVLW 0xNN. This is because the 14 bit core parts begin execution at address 00, not at top of memory. You can retrieve the calibration constant at any time during program execution by CALLing the last program memory location. Do note: the emulator does not like you calling the calibration location because it is unprogrammed. I have a compile time flag that replaces that call with a movlw 0xNN instead. dwayne Dwayne Reid <.....dwaynerKILLspam.....planet.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 hint: To leave the PICList EraseMEpiclist-unsubscribe-requestspam_OUTTakeThisOuTmitvma.mit.edu

I have the same problem with a 12 PIC. The "goto intlevel0" instruction in the last program memory location, produced by the compiler, goes onto the existing "retlw 0xxx" in the OTP parts. The retlw binary opcode is "1101xxkkkkkk", and the goto "101kkkkkkkkkkk". So, once programmed the part with the code produced by the compiler, the resulting opcode will be "100xxxxxxxxxxx". This is a "call" instruction... {Original Message removed}