As the capability of spacecraft microprocessorsrnincreases, there is a growing trend for distributing thernspacecraft control applications amongst remoternterminals on the bus. This trend is seen both inrnpayloads and in the spacecraft sub-systems.rnOn the one hand, there is an increase in the proportionrnof data packet traffic on the onboard bus. On the otherrnhand, as remote terminals become more "intelligent",rnthey expect better services from the onboard bus. Inrnparticular, they expect to be able to access the bus torntransfer data packets on demand, and many modernrnsoftware architectures are based on messagingrncapabilities, where applications communicate withrneach other variable length messages that arerngenerated asynchronously.rnThe increasing "intelligence" in remote terminals,rntheir demands for more comprehensive communicationrnservices, and the need to support multi-busrnheterogeneous architectures, result in an increased usernof higher level protocols and services across multiplernand different onboard buses.rnThis paper presents the ongoing effort realised withinrnthe ECSS CAN working group on defining thernnecessary services and associated data link protocolsrnto standardise the usage of CAN bus in spacernapplications.
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