A brake control unit for a railway vehicle having first and second cores. The first core is responsible for brake control functions and the second core is responsible for communications. A switch controls communication between the second core and a communication bus on the railway vehicle to safeguard the braking function of the first core. The second core only has write access to the communication bus when enabled by the first core, which first core determines whether the system is in a defined safe state to safeguard the braking function. This reduces the testing requirements for new communications software.