Development of Network Gateway Between CAN and FlexRay Protocols For ECU Embedded Systems

This paper presents a network gateway between the CAN and FlexRay protocols for ECU embedded systems. Flexible gateways are necessary for implementing several functions to avoiding the need for increased clock speed. This gateway system is based on a second internal control unit, which can be implemented as a RISC or a specialized finite state machine and use combined message buffer RAM. The control unit is used to lessen the interrupt burden of the main CPU and to reduce the required CPU performance, while message buffer RAM is used to store all messages transmitted and received. It requires a high system frequency to guarantee the transfer of data between two or more networks in real-time and to assure data integrity. To compensate for the limited functionality of the modules, the control unit requires greater program memory capacity, for storing the complex routing information. This gateway system is based on proven communication controllers, expanded with a gateway interface. These communication controllers are linked by an independent CPU data bus structure that enables the transfer of messages. The data flow between the modules is controlled by an application specific Gateway Unit that provides all control signals. This unit consists of special function registers or of an independent CPU finite state machine. Due to the special gateway interfaces, which allows concurrent CPU and Gateway Unit request to the same cell, semaphores and flags are not necessary. This maximizes the flexibility of the module.