Hello,

I have trying to download the software through JTAG connector into PCBA, where the PCBA working fine. But, I got an error in the UDE says that the micro-controller is can't able to connect to the UDE.

So, I have investigated on between the PCBA where it is used for software download and another new PCBA, and found that there was a hug resistance between the JTAG pin and GND.

Resistance between JTAG pin and GND is kilo ohms resistance for the PCBA (where it is used for software download)
Resistance between JTAG pin and GND is hundred ohms resistance (five times higher value than the kilo ohms) for the new PCBA.

My question is that, why there was huge resistance values are differs and what is the reason behind it? please, could you explain this behavior..

 

You will need to give some details so that someone has a chance of helping you. For example the schematic of the PCBA, the device you are trying to program, the programmer and software you are using to program.

Les.

 

If you are measuring resistance between two pins using an ohmmeter the reading is not reliable and of little use (except for detecting a dead short).