A computerized method of creating a circuit logic model of a VLSI device, comprising mapping a plurality of logic function patterns of one or more circuits of a VLSI device through a plurality of probe iterations and generating a circuit logic model of the circuit(s) by reconstructing a logical function of a combinatorial logic of the circuit(s) based on analysis of the logic function patterns. Each of the probe iteration comprises switching between scan shift mode and functional mode of the VLSI device such that while the VLSI device operates in scan shift mode register(s) associated with the circuit(s) is accessed and while the VLSI device operates in functional mode external pin(s) of the VLSI device associated with the circuit(s) is probed and mapping a respective one of the logic function patterns according to a logic state of one or more bits in the register(s) and/or the external pin(s).