elektryk
Joined: 25 Apr 2002
Posts: 106
Location: POLAND
|
 17 Apr 2008 2:33 Pin connection test in programmers. |
|
|
|
Hi, I am not sure if it is right category, but I this one is best.
My question is about, function build in advanced commercial programmers (like Elnec, Velon, etc). Most of them are able to detect connection between programming socket and chip pin. How it is made? I think it is done, by disconnecting power from chip (Vcc) and putting Vcc on tested pin. Because all "new" (I guess from 1980) chips has protection diodes on any pin from pin to Vcc and GND, if any pin is powered with voltage greater than Vcc current flows thru diode and on Vcc pin non-zero voltage appears. This is my teory, which I am testing on real circuit. When I put real diode (something like 1N4148 or simmilar) voltage apears, but when I put any logic pin, voltage on Vcc is floating about 0 (no more then 0.01V). So, how it is made in commercial programmers? I had tested ELNEC device, and if I plug adapter into socket, pin connection detecting still works, so it is not made mechanical "double" contact socket.
|
|
