Tracing signals

To trace signals around the circuit, you need the JTAG Chain Debugger, an oscilloscope and a circuit schematic.

First make sure the current Pin Mapping and Test Reset Sequence are correct for your circuit. You can either select a predefined mapping, set the mapping manually, or load a pre-defined pinmap by selecting File | Load.

There are then two ways of tracing signals around the JTAG chain. You can do one or the other - not both at the same time.

• Loop ID Codes: XJTAG will continuously try to read the ID codes of the devices in the chain, causing regular activity on all four of the JTAG pins on the XJLink.
• Toggle Pins: XJTAG can toggle any of the pins (driving high and then low) that is set as an output. You can toggle more than one pin at once, in which case they will change between high and low at the same time.

Having established your debug signals, you can then trace the signals around the JTAG chain using an oscilloscope and the circuit schematic.