>
> Hi ev'rybody,
>
> I've troubles getting a home-built Tait-style 16F84 programmer to work,
> although I believe the hardware (parallel port, D0, D1 for programming, ACK
> for readback) to be correct (correct voltage of _MCLR during programming,
> correct Vdd and Vss, correct "0" and "1" levels at RB6 and RB7).
>
> I use the circuit with David Taits PP.EXE, and it verifies fine in debug mode
> (PPDEBUG=1, readback is o.k.), but during programming the very first word of
> WALK.HEX, PP.EXE stops with "error: read 03FF, expected 0186" or something
> like that. Now I'm wondering if not the programmer, but the 16F84 chip itself
> is faulty?
>
> Does anyone have a hint where I could start searching for the problem?
> I already tried various settings of PPDELAY and PPSETUP, but nothing works.
> Unfortunately I just have a logic probe, but no scope for testing.
> How can I test the 16F84 chip to be "good" or "bad", or further verify the
> programmer hardware without a scope?
>
> Thanks for your help,
> Franz

> -----Original Message-----
> From: Franz Fasching [SMTP:.....faschingKILLspam@spam@AUSTRIA.IBM.COM]
> Sent: Tuesday, June 01, 1999 9:03 AM
> To:   PICLISTKILLspamMITVMA.MIT.EDU
> Subject:      16F84 Tait-style programmer troubles
>
>  > From:    Jeff Webster <.....webstejKILLspam.....MINDSPRING.COM>
>  > Greetings:
>  >   You don't say how you power the circuit.  I have had similar problems
>  > when using Tait-style programmers under battery power when the
> batteries
>  > get weak.  It will read the PIC fine, and erase it fine but you will
> get
>  > errors when you try to program it.
>  >
> That should be no problem; I use a stabilized lab power supply set to 13 V
> for
> Vpp, and a 7805 for getting Vdd. But as I said, the very first read to
> verify
> the very first word programmed fails with "read 3FFF, expected
> 0186".
>
> So how can I verify that either the circuit or the 16F84 is bad?
> Any hints appreciated!
> Thanks,
> Franz