The project I am working on for my company needs to test a BGA Coldfire 5485 with Boundary Scan ( IEEE-1149.1) or JTAG. After pulling MTMOD0 high and only one device itself in the chain, I was able to run Boundary Scan test on it without any problem. However, after I attached it at the end of another JTAG chain on the board including one Xilinx FPGA and two Intel Ethernet chips. The Boundary Scan chain even couldn't be recognized. All the wirings are right. Put scope to look at it. There is something on Coldfire pin A15 (TDI), but nothing coming out of pin D17 (TDO). It seems Coldfire doesn't like to be in a JTAG chain with other devices.
Does anyone have any experience on this?