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PICList Thread
'16C84 Erasing and Odd Program Modes'
1998\01\30@120511 by Al Williams

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Microchip says to remove the CP bit and erase a 16C84, you Load the Config
image with bit 4 set, Send a command 1, a command 7, a command 8 (program),
delay 10ms, then send command 1 and 7 again.

What does command 1 and 7 do? Anyone know? The reason I am interested, is my
programming software (homebrew) is acting funny. Doing the previous sequence
erases the program memory but not the data memory. If you load something
other than all 1's in the config register, the PIC writes that value to all
memory. Also when I program my fuses, it seems to shift the PC over by one
each time I program (that is I start reading from location 1 instead of 0).
Very odd.

I suspect I am not shifting out commands properly, but I can't prove that as
yet. The high-level stuff is OK because using a different driver for
LudiPipo-style interface works great. But my custom hardware and driver
seems to work fine except for the erasure of data memory and the upset when
programming the fuse word.

Anybody see anything like this before?

Regards,

Al Williams
AWC
*Solderless Stamp Prototypes at http://www.al-williams.com/awce.htm


'16C84 Erasing and Odd Program Modes'
1998\02\01@155705 by wouter van ooijen
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> What does command 1 and 7 do? Anyone know? The reason I am interested, is
my
> programming software (homebrew) is acting funny. Doing the previous
sequence
> erases the program memory but not the data memory.

In my experience the sequence described by microchip erases code + config
memory,
and in addition it erases data memory if (and only if) the code protection
bit was set.

1998\02\01@194957 by Al Williams

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Ah... I hadn't noticed that. So that means my erase is probably working.
Then the only problem is that if I burn the fuse word, when I do a read
after a reset, I read location 1 instead of 0! I can do everything except
the burn of the fuse (even IDs) and it comes up with location 0. If I burn
the fuse, I get location 1. Very strange. Oh well, I'm sure I will work it
out.

Thanks for the insight.

Al Williams
AWC
*Solderless Stamp Prototypes at http://www.al-williams.com/awce.htm (works
for PICStics too).

{Original Message removed}

1998\02\03@142535 by rtszib

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Al Williams wrote:

> Ah... I hadn't noticed that. So that means my erase is probably
> working.
> Then the only problem is that if I burn the fuse word, when I do a
> read
> after a reset, I read location 1 instead of 0! I can do everything
> except
> the burn of the fuse (even IDs) and it comes up with location 0. If I
> burn
> the fuse, I get location 1. Very strange. Oh well, I'm sure I will
> work it
> out.
>

Dear Al

This problem is not described in 16c84 programming specs. But an answer
is in progamming specifications of other PIC (do not remember which
exactly). I faced with it when built my own programmer. The problem is
in entering programming mode. Being more precise - voltage on MCLR pin
rises not as fast as it should. This result in PC counter increments and
you read location 1 instead of 0. As for configuration memory this does
not matter since you use additional command to enter this mode which
sets PC to 2000. When configuration word is not programmed the
oscillator is configured fo RC and does not work with crystal.when you
programm it you get this fucking increment.
There are two ways to avoid those increments: 1 slow down your PIC or
stop it (in case of in-circuit programming). 2 change your MCLR
circuitry which applies 12 V ( open collector with 10 K pull-up resistor
which I see on many programmers is not enough for in-circuit programming
even if PIC run @ 4 MGz). I redused pull-up to 1 K and this work up
until 10 MGz.

Regards
Vassili

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