How to operate a JTAG PORT

Hello
  I would like to know how to operate a JTAG PORT to drive the entire
scan system? Is this risky?
Any responses greatly appreciated

Thanks
krithiga

krithiga81@yahoo.com wrote:
> Hello
>   I would like to know how to operate a JTAG PORT to drive the entire
> scan system? Is this risky?
> Any responses greatly appreciated
> 
> Thanks
> krithiga
> 
How do you define "the entire system"  ?

If you mean, drive a "CPU" and an "FPGA" and a "???".

Then, yes it is risky.

The software to drive any jtag device may not be able to drive all jtag 
devices in the chain.

donald

Hello
  By system, I mean a CPU , FPGA. Why is it risky?

Thanks
krithiga

krithiga81@yahoo.com wrote:

> Hello
>   By system, I mean a CPU , FPGA. Why is it risky?
> 
> Thanks
> krithiga
> 
The part of my last message you ignored:
 >>Then, yes it is risky.

 >>The software to drive any jtag device may not be able to drive all
 >>jtag devices in the chain.

So what part of this statment did you not understand ?

If two devices are on the same chain, the software for device two must 
get thru device one.

Did this statment make sense ??

If it does not make sense to you, then study up on JTAG chains.

Donald