Abstract: A vehicle safety electronic control system (11) including master and slave microcontrollers (12, 13). The master microcontroller (12) is connected to a TDMA network bus, and the slave microcontroller (13) is connected to the master microcontroller (12) via a general purpose input/connection (14). Both microcontrollers (12, 13) are configured to operate schedule table based execution, and each has a respective synchronization counter. The master microcontroller (12) is configured to update its synchronization counter in response to a primary synchronization signal (19) from the network bus (10), and to issue a corresponding secondary synchronisation signal (20) to the slave microcontroller (13) via the general purpose input/output connection (14).