Why the isp software can't read the signature of the at89s52

problem in isp.

Al;ways put a 10uF and 0.1 disc cap across pins 40 and 20, that too as close as possible.then ensure that the signals are direction buffered from the LPT port by using AND 74HCxx buffers. The cable leading from the buffered LPT pins to the programmer be kept mot more than 12" long. Thenyou may also try a 100ohm seires resistor and decoupled by 220pF on the MOSI pin cloase to the chip mounting socket.then ensure that the programming speed is at or less than the 1/16th of the crystal oscillator used.
with these mods the programer should behave better and most uncertainities will be overcome.

Sarma

Re: problem in isp.

@fala, I think you lack the experience to use a bread board in the correct way :twisted:
That board is over 10 years of age and like I said I never experienced bad connections with it.

Please also check this one: https://en.wikipedia.org/wiki/Image:Breadboard_complex.jpg
and learn to use a bread board not abuse it

Cheers...

Re: problem in isp.

mcs51mc said:

@fala, I think you lack the experience to use a bread board in the correct way :twisted:
That board is over 10 years of age and like I said I never experienced bad connections with it.

Please also check this one: https://en.wikipedia.org/wiki/Image:Breadboard_complex.jpg
and learn to use a bread board not abuse it

Cheers...

Click to expand...

Well it is a bit disconserning that you do trust a breadboard's connections. It is basically just two copper plates that holds the connection. They can bend and make no connection. Point is you just cannot trust a breadboard connection, especially if it is used for a few years already. I always check the connections first on my breadboard circuits and it is usually the problem. If you want to be sure of a connection use solder, or let's say 90% sure at least.

Regards

Nic

Re: problem in isp.

ScratchBuild said:

Well it is a bit disconserning that you do trust a breadboard's connections. It is basically just two copper plates that holds the connection. They can bend and make no connection. Point is you just cannot trust a breadboard connection, especially if it is used for a few years already. I always check the connections first on my breadboard circuits and it is usually the problem. If you want to be sure of a connection use solder, or let's say 90% sure at least.

Regards

Nic

Click to expand...

Exactly! even if you solder it you will get maximum of 90% reliability. if you also precisely check the soldered pin visually(with a good magnifier)you will get 95% and if you check it with ohmmeter you will get ~99% and still have to pray for the other 1%.
Once a customer called me and reported a malfunctioning device that had bought from me. After checking voltages I notices an output from a through-hole 7815 is float and has no voltage. I checked it visually nothing seemed wrong. the pin had been soldered from bottom side of the board, I also soldered it from top to the pad again No voltage I checked it with ohmmeter and made sure that pin is connected electrically to top pad but when I checked the bottom pad it had been disconnected to the pin. It was extremely unusual possibly the pin had been broken somewhere within the hole, possibly because 7815 had been bended so heat sink have better ventilation!