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'[PICLIST] Programming Woes PIC16F877'
|Yes, that old chesnut...again.
I have looked back through the last few weeks of comments from the likes of
Jim Robertson amnd Tony Nixon, but the particular problem I have dosen't
seem to have cropped up yet AFAICT.
I have a product using a 16F877 which is programmed via ICSP using a Promate
programmer. RB3 has been asigned the role of an SPI clock, and during
programming is actually floating, which isn't generaly a good idea it seems.
However, until now we have *NEVER* had a problem. All chips have programmed
and verified at high/low voltages. The problem I am seeing is that after
programming some chips once, I can't program them again. The fuses we
normaly use for programming are HS osc, brownout enabled, watchdog enabled,
power on timer enabled, all code protect disabled, low voltage programming
disabled, debug mode disabled.
Having tried to program the part, MPLAB reports a failure. Further
investigation shows that none of the code or data eeprom memory has been
programmed and the CPD config bit is somehow set. The Promate seems to
perform a bulk erase at the start of the programming cycle, but it does not
erase anything! I can read back all the original data from the chip. In
fact the only things programable on these parts are the config bits apart
from CPD which seems to be remaining set (although it should not have been
I have tried everything I can think of, including grounding RB3 during
programming and grounding the osciliator pins. I have verified the
programming voltages: clock, data and Vpp and all are correct. I now have 4
of these parts (which are SMD devices in a very small product so not too
easy to replace). Any ideas?
Puzzled from Paignton.
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Michael Rigby-Jones wrote:
> Yes, that old chesnut...again.
> I have tried everything I can think of, including grounding RB3 during
> programming and grounding the osciliator pins.
OSC2 is an output, so I wouldn't ground it, just OSC1.
This probably isn't the source of your problem though.
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Having found our ICD, I connected it up, and it programmed the device
perfectly. I wasn't convinced but a verify confirmed it. So then I
reconnected it to the Promate and tried to read it. All the program data
came back as 0x0FF (not even 0x3FF). The device programmed with the ICD
worked perfectly. The Promate continues to work fine with other parts, it's
just these few devices it will not program or read. I have checked out the
ICSP cable and it's fine. The FAE is down in a couple of days so I'll let
him figure it out!
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