UPPERBUS: Ein Bit-Serieller Echtzeitbus mit 560 MBIT/S — Glasfaserübertragung

UPPERBUS is an ultra wideband, bit-serial computer link bus that operates on the basis of the Slotted Ring Protocol (SRP). The UPPERBUS features a gross data transmission rate of 2 x 280 megabits per second. The SRP is a “fair” protocol which guarantees that in the worst case, i. e., at a 100% bus load, a given maximal wait time for bus access is never exceeded. Therefore, the SRP is particularly suited for realtime applications. The SRP is based on the notion of fully synchronous data transmission, operating with fixed time slots and fixed packet length. This feature of the UPPERBUS renders it particularly appropriate for applications of computer integrated manufacturing and process control, since it allows some of the time slots to be reserved for special services (e. g., the instantaneous transmission of alarms). The very high data rate of the UPPERBUS requires extremely fast bus controller hardware, which in the existing version consists of a bit-slice flow control processor in connection with ECL memory and a set of ECL gate array chips that can handle a stream of 280 megabits per second. For fault tolerance reasons the UPPERBUS controller is designed to handle two such bit streams, which are either multiplexed onto one fiber optics cable or transmitted via two separate cables, depending on the degree of fault tolerance one wants to obtain. Consequently, in the fault-free case the effective data rate is 2 x 280 = 560 megabits per second. The UPPERBUS controller performs all the functions of the levels 1 through 4 of the OSI protocol hierarchy. The SRP philosophy, the properties resulting from it, and the technical solutions employed in the UPPERBUS are discussed, and areas of application are outlined.