hello everyone

ive decided to build this programmer a while a go and now its done and it dosent work ! , http://www.semis.demon.co.uk/Pics/PICmain.htm a tait variant parallel port programmer, all tests specified on the website was done successfully but i cant program a F84A or the F628A it writes the code and

gives me a "verify failed at address 000h !" error then when i close icprog and open it again to read the pic its blank and full of 0x3FFF
so i thought to myself that the things ive done must cause it not to work so heres what ive changed

* swapped the 7406 with a 7404 since i broke two pins from the 7406 IC trying to yank it out of the socket, assuming 7406 ~= 7404 anyone here knows whats the difference ?

* i ignored both 1nF capacitors that is just after the data line and the clock line cause i dont have any 1nF or closer value

also ive tried to plug it in directly to the parallel port but that dosent help either, and i had noticed that both VCC and VPP(MCLR) led indicators go off during programming/reading

i saw some post a while ago on this forum or some other forum cant really remember, it said that RB10 pin or something like that has to be 0V in order to program a chip can some please remind me of what it was

please anyone help me got to learn PIC micro

 

The 7406 has open collector outputs and is the correct part.

I don't use any capacitors on those lines.

RB10?


Have you configured IC-Prog for you programmer? click "Settings" and "Hardware" and say which signals are inverted.

 

Why not build the very simple JDM programmer
http://www.semis.demon.co.uk/uJDM/uJDMmain.htm

__________________
Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com

 

Let this to be a reminder for v1r05 & others who wants to build similar programmer.

One cannot use other buffer/inverter parts to replace 7406 or 7407 because they are chosen for their open-collector properties. Non open collector type will simply not work. I know they are hard to get now.

For the 16F628A, one has to ground pin10(RB4/PGM) to disable the low voltage programming (LVP) feature which is enabled on the chip from the factory.

__________________
L.Chung

 

well thats good thanks

well i got a 7407. and eng1 ignored those small capacitors then it should work without problem i downloaded the 7407 datasheet and it dosent look like it inverts the input and i guess i dont have to invert any line from IC-PROG

am i right ?

blueroomelectronics, thats will probably be next if this fails

thanks alot guys

 

btw during programming does the MCLR has to be at 13.Xv or and what about vcc should it be high or low ?

thanks again

 

The 7407 is a good replacement. By the way, you can use the hardware check feature and measure the volatges with a multimeter.

EDIT: see the attached picture, are you using these settings?

Attached Images

7407.png (594 Bytes, 0 views)

 

VPP at MCLR pin should be 12V or higher during programming.

The requirement of 13.0V or higher is dated back from many years ago. With modern PIC parts, I have absolutely no problem using 12V to 13V for VPP.

If one checks the corresponding PIC datasheet, it does give both maximum and minimum Vpp threshold voltage. Some PICs has max Vpp of only 12.5V. The original ICD2 changes its VPP voltage accordingly to suit.

Will one damage those PIC using higher VPP voltage? You try and tell us.

__________________
L.Chung

 

ok, it works now but with winpic not icprog and i can only program a brand new F628 !A, F84A and F628A are not programmable probably they are fried during earlier tests with some other programmer 7.40$ up in smoke and no buzz

thanks again guys