JTAG Switcher is open source VHDL code intended to be implemented in an FPGA.
JTAG Switcher provides a solution how to connect multiple JTAG TAPs (JTAG Test Access Ports) from multiple chips on a PCB (Printed Circuit Board) to a single board wide TAP to which a suitable tool (like a JTAG debugger) might be connected.
The approach with JTAG Switcher is to connect multiple JTAG TAPs from multiple chips on the PCB in a point-to-point fashion to an FPGA which contains the JTAG Switcher circuitry. The board wide JTAG connector is connected to the same FPGA. The JTAG Switcher circuitry routes the signals from the board wide JTAG connector to the various JTAG TAPs of the chips on the PCB.
JTAG Switcher was implemented at Lauterbach.
Detailed documentation can be found here: JTAG Switcher White Paper JTAG Switcher presentation JTAG Switcher reference manual