A control apparatus for a powertrain system comprising an engine and two electrical machines operably coupled to a two-mode compound-split electro-mechanical transmission is provided. It includes a system controller and two motor control processors. The system controller communicates with the motor control processors via two high speed communications buses and directly-linked serial peripheral interface buses. The motor control processors control flow of electrical power between the electrical machines and an electrical energy storage device. A second control device is operable to control the engine, preferably to control torque output. The internal combustion engine preferably has a crank position sensor which is signally connected to a dedicated input to the second control device and to a dedicated input to the system controller of the first control device.