Abstract: The invention relates to an integrated circuit, comprising a number of independent clock domains. Seam circuits are provided in the interface signals paths between the clock domains in order to be able to isolate clock domains from each other during testing. Each seam circuit comprises a feedback loop having a multiplexer and a flip-flop feeding a first input of the multiplexer, a second input of the multiplexer being connected to the seam input, an output of the feedback loop being connected to the output; so that a first state of the multiplexer allows loading of a data bit in the feedback loop via the seam input, and a second state of the multiplexer freezes the data bit in the feedback loop.