Hi Henrik

Bad news Im afraid. I updated this machine to MPLab 7.30 and my programmer says PICSTART Plus Firmware Version 4.40.1.

Tried the 18F2431 and 18F4431 and failed with all three chips of each type.

I couldnt find the 4550s after putting them somewhere safe when I tidied up the other day but did find something else that I had lost ^H^H^H^H put away safely

Successfully programmed 3 18F4520s with no hesitation.

Now the bad bit. A Googling session gave me the following information....

from http://forum.microchip.com/tm.aspx?m=189398

I have also had trouble programming the 18F2431 on Tech-Tools programmers. They (Tech Tools) have confirmed the problem, but have no solution. They are removing this part from the list of compatible parts from their list. They say that the Microchip programming equipment does not program this part.


from http://forum.microchip.com/tm.aspx?m=107927

The 18Fxx31 and several other devices in this family require the use of a capicitor between Vdd and Vss to slow down the rise time. Some will not Erase, thus will not program if not blank. PM 3 is also subject to this problem.

This workaround can be found in the Readme for PicStart Plus but has been further updated to include other devices that were found to have this problem:

Some devices require that a 0.1uF bypass capacitor be placed
from the VDD pin to the VSS pin of the device to successfully
program the device. If programming failures still arise,
try increasing this value incrementally to a maximum of 10uF.
The parts affected are:

PIC16F737 PIC16F747 PIC16F767 PIC16F777
PIC18F1220 PIC18F1320 PIC18F2220 PIC18F2320
PIC18F2331 PIC18F2431 PIC18F2410 PIC18F2420
PIC18F2455 PIC18F2480 PIC18F2510 PIC18F2515
PIC18F2520 PIC18F2525 PIC18F2550 PIC18F2580
PIC18F2585 PIC18F2610 PIC18F2620 PIC18F2680

For devices such as the 18Fxx31 which have power supply (Vdd and AVdd)
and ground (Vss and AVss), all pins must be used in order for these
devices to program.

Now the REALLY BAD NEWS.....

tried all that and it still didnt work. I started off with a 100nF cap on each set of supply pins and that didnt work so went the whole hog and stuck 4.7uF on each set of pins. At that point I got the following error message when I tried to program.

Program Memory or EEPROM Data is protected. Reprogram
the entire part. If "Auto select memory areas and range"
on the Memory Ranges tab of the programmer settings
is enabled, it must be disabeled before proceeding..

Removing the caps took me back to the original "going through the motions" before failing verification. Decided to go a bit more gently with the caps and used a 1.0uF. Still failed. Added a 100nF as well... still failed.

Decided to go for a 2.2uF and got the "protected" message again.

Reverted to the smaller caps and checked the voltages while programming. 4.97v on one set of pins, 5.01 on the other set. Wasnt sure if this was because only one set were powered and the lower voltage was fed through the PIC so I removed it and attempted to check the voltages.

Without a PIC you instantly get the "protected" message again but I did see a breif change on the multimeter on both sets of pins.

Dont know what to do now