In this manuscript, we propose a configurable hardware device in order to build a coherent data log unit. We address the need for analyzing mixed-criticality systems, thus guaranteeing the best performances without introducing additional sources of interference. Log data are essential to inspect the behavior of running applications when safety analyses or worst-case execution time measurements are performed. Furthermore, performance and timing investigations are useful for solving scheduling issues to balance resource budgets and investigate misbehavior and failure causes. We additionally present a performance evaluation and log capabilities by means of simulations on a RISC-V use case. The simulations highlight that such a data log unit can trace the execution from a single- to an octa-core microcontroller. Such an analysis allows a silicon developer to obtain the right sizings and timings of devices during the development phase. Finally, we present an analysis of a real RISC-V implementation for a Xilinx UltraScale+ FPGA, which was obtained with Vivado 2018. The results show that our data log unit implementation does not introduce a significant area overhead if compared to the RISC-V core targeted for tests, and that the timing constraints are not violated.