Patent ID: 6886110

Claim:
A method for emulating individual devices in a multiple device chain, said method comprising: obtaining the topology of the chain; selecting one device within the chain by generating a selection instruction and sending the selection instruction to the chain; placing at least one other device within the chain into bypass mode; sending emulation instructions to the chain, wherein the emulation instructions bypass the at least one other device and are executed by the one device; wherein the individual devices comprise JTAG devices and the chain includes a boundary scan chain; and wherein the selection instruction comprises; an Instruction Register Header field to retain the number of instruction register bits upstream of the one device in the scan chain; an Instruction Register Tail field to retain the number of instruction register bits downstream of the one device in the scan chain; a Data Register Header field to retain the number of devices upstream of the one device in the scan chain; a Data Register Tail field to retain the number of devices downstream of the one device in the scan chain; and a Command field to retain a command for the one device.