While the semiconductor industry makes progress in every year integrating more components on a single die and stacking them, manufacturers face great challenge as the dissipated power densities reach the limits of current cooling solutions. Since peak temperature and temperature gradients influence the functional behavior of the ICs, co-simulation of the logic function and thermal behavior can help to assess the overall performance of the system at various stages of the design flow better. Logi-thermal simulators (extending the concept of the transistor level electro-thermal simulation of integrated circuits to higher abstraction levels) can predict the dissipated power based on the switching activities of the system, consider the local temperature dependence of certain circuit properties and calculate the temperature distribution across the chip consistently.This paper presents a logi-thermal simulation framework that allows to couple logic simulators and thermal solver engines to facilitate the co-simulation of high level functional and thermal behavior of digital circuits, both on gate level and register-transfer level. We show examples by integrating SystemC with the thermal simulator SUNRED, and comparing the results of a gate level logi-thermal simulation and logi-thermal simulation obtained with the register-transfer level description of the same system.