I have 2 devices, a Spartan 3 and a Spartan 6. I am trying to configure both of them through JTAG. One way to do this is to daisy chain the devices and use boundary scan. However , one thing I still don't understand is how do I select which device in the chain I want to program in Xilinx? Where is the option for this?
Second this is a proto board and the focus is on the ease of debugging. Will daisy chaining like this cause problems? Is there any easy way to put a single jumper to switch the JTAG pins between FPGA's or is it better to have 2 14 pin connectors and keep removing the programmer header and putting it back in?
What exactly needs to be done at the PCB design level? Is shorting the TMS,TDI,TDO,TCK from different FPGAS sufficient ?