Post by thread:Problem with 12c509 actually working.

I bought several of the OTP parts of the 12C509. I am using Picstart Plus, with MPLAB-C 1.21. Its a simple program that I have run on many different chips, but this one just seems to sit there with no sign of pin change. The issues (as I understand them) Set INTERNAL RC Set Internal Reset clear OPTION bit 5 and 6 use the __TRIS macro to set bit 0 and 1 as outputs Whatelse is there? I use the Pins a Output , but they never change. Is there something I need to know about this internal clock? What is th e OSC Trim byte for? Thanks in advance John Craft John A. Craft (601)689-8100 Voice Vice President, Sr. Analyst (601)689-8130 Fax Nation Computer Services, Inc. http://www.ncs-ssc.com MSAAP Bldg 9110 spam_OUTcraftTakeThisOuTncs-ssc.com Stennis Space Center, MS 39529

On Sat, 6 Dec 1997 18:01:16 -0600, you wrote: >I bought several of the OTP parts of the 12C509. I am using Picstart Plus, >with MPLAB-C 1.21. > >Its a simple program that I have run on many different chips, but this one >just seems to sit there with no sign of pin change. > >The issues (as I understand them) > > Set INTERNAL RC > > Set Internal Reset > > clear OPTION bit 5 and 6 > > use the __TRIS macro to set bit 0 and 1 as outputs > > Whatelse is there? I use the Pins a Output , but they never change. > > Is there something I need to know about this internal clock? What is the >OSC Trim byte for? Exactly that, i.e. to trim the oscillator to a nominal 4Mhz The first instruction (at location 0) should be a MOVWF OSCCAL to load the factory calculated value for the particular chip to the osccal register. See earlier posts concerning erased cal values in JW parts. Even without this, programs should still run, albeit at the wrong speed. ____ ____ _/ L_/ Mike Harrison / White Wing Logic / .....wwlKILLspam@spam@netcomuk.co.uk _/ L_/ _/ W_/ Hardware & Software design / PCB Design / Consultancy _/ W_/ /_W_/ Industrial / Computer Peripherals / Hazardous Area /_W_/

{Quote hidden}>I bought several of the OTP parts of the 12C509. I am using Picstart Plus, >with MPLAB-C 1.21. > >Its a simple program that I have run on many different chips, but this one >just seems to sit there with no sign of pin change. > >The issues (as I understand them) > > Set INTERNAL RC > > Set Internal Reset > > clear OPTION bit 5 and 6 > > use the __TRIS macro to set bit 0 and 1 as outputs > > Whatelse is there? I use the Pins a Output , but they never change. > > Is there something I need to know about this internal clock? What >is the >OSC Trim byte for? > You don't need to know anything about the OSCCAL value. If you do nothing the chip will work, but not necessarily at 4MHz. On powerup, the chip always executes a 'MOVLW' instruction, though, loading W with the appropriate value for trimming the Osc. Your first instruction in your program should always be 'MOVWF OSCCAL' when running with the internal RC. Jim