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'[PIC]: 16CE625 that won't start?'
2001\01\08@214648 by John Hansen

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My previous development experience has been mostly limited to the flash
parts, so I may be missing something.  I have a simple circuit put together
on my breadboard that simply feeds 5 volts to an 18 pin PIC and attaches a
4 Mhz ceramic resonator to the appropriate pins.  There are no other
connections (I stripped this down to try to eliminate sources of potential
error).   The program I am using simply sets the TRIS registers to outputs
and then takes all of the pins high.  When I plug a 16F84 into this circuit
it performs as expected.  The pins are high and my frequency counter reads
about 4 MHz on the resonator pins.  When I plug a windowed 16CE625 into the
same position, I get nothing.  Not only are the pins not high, but there is
no reading on the frequency counter.  From the data sheet it looks like
these chips should be pin compatible.  Is there some trick to getting a
16CE625 to run?  I've tried this with 2 different windowed 625's with the
same result in both cases.   The 625's are new -- came from DigiKey
today.  Thanks in advance for any assistance.

John Hansen

Here's the code for the 16CE625 version.  My programmer verifies it as
being in the chip.

                 list                  p=16CE625
                __CONFIG   0X3FF9
                org                 0x00
               movlw           0x00
               clrf                0X05
               movlw           0x07
               movwf           0X1F
               BSF              0X03,5
                MOVLW       0X00
                MOVWF       0X85
               MOVLW       0X00
               MOVWF       0X86
               BCF              0X03,5
               MOVLW       0X1F
               MOVWF       0X05
               MOVLW       0XFF
               MOVWF       0X06
DONE    GOTO    DONE
              END

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2001\01\09@064217 by Stuart O'Reilly

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Do a read on the chip and make sure the osc setting is on xtal and not
rc. I've been having this problem reccently and I can do a program and
verify and all looks ok but if I read the chip it then shows me the osc
is set to rc and not xtal despite the fact that i programed it as xtal.
Regards
Stuart

John Hansen wrote:
{Quote hidden}

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2001\01\09@065803 by dr. Imre Bartfai

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Hi,

it is a VERY BAD practice not to use the standard naming convention of the
register. I strongly advice to use standard names, especially, if you want
somebody (including you) to understand the code.

And the answer (I think, at least):

That pins are set up as comparator inputs. You must set at first

       movlw   7
       movwf   CMCON

to disable the comparators.

Regards,
Imre


On Mon, 8 Jan 2001, John Hansen wrote:

{Quote hidden}

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2001\01\09@090746 by Olin Lathrop

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> When I plug a 16F84 into this circuit
> it performs as expected.  The pins are high and my frequency counter reads
> about 4 MHz on the resonator pins.  When I plug a windowed 16CE625 into
the
> same position, I get nothing.

Did you cover up the window?  I've had windowed parts that couldn't start up
the oscillator until the window was covered.

What oscillator setting are you using?


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, spam_OUTolinTakeThisOuTspamembedinc.com, http://www.embedinc.com

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