Stratix III 's JTAG Chain Problem

[Altera_Forum]

Dear All, 

I have problem in JTAG chain of Stratix III.  I have a board which uses 2 FPGAs Stratix III (EP3SL200H780C4N). They are connected in JTAG chain. I also send the JTAG chain to you for review. :confused:Here are problem: 1. I can not program for FPGAs with JTAG chain 2. I program for FPGA2 first, and then program for FPGA1. It is OK. But if I program for FPGA1 first, and then program for FPGA2 --> FPGA1 be reseted. Could you please help me to find out the problem ? Could you also suggest me the solution for this problem? Thanks

[Altera_Forum]

I can not open the zip file. 

 If you try to keep config low after programming ?   Hans

[Altera_Forum]

The zip file seems to be damaged, can't open it too 

 do you have more informations about how the fpga's are connected to the jtag and what about the addition signls like nConfig and others.

[Altera_Forum]

I re-send the JTAG chain as pdf file to you. 

I also send the Config connections for both FPGAs to you for review.  Thanks Bao Khanh

[Altera_Forum]

Failure of JTAG operation in dependence on activity of other design parts can be a problem of crosstalk between JTAG and other on board signals. In this case, you should check for possible interferences with the nconfig input.  

 A power supply drop would be another possible explanation.