Calculation of Control Codes Delays in Onboard SpaceWire Networks

This article is a continuation of the work, which describes the development of routes' calculation for information flows and their delays' calculation. That component is a part of software complex for onboard spacecraft computer networks design SANDS. This article is focused on delays' calculation of control codes propagation in SpaceWire network (time-codes, distributed interrupts and acknowledgment). The control codes delays' calculation is the one of many functionalities of the SANDS component for route's evaluation. To maintain proper network operation, it is very important to make the synchronization among all devices in the network and timely notify one or group of devices about critical events. To solve this problem control codes were developed. The wrong control code propagation delay estimation may lead incorrect working of network. Analytical model is provided in this article to calculate propagation time and delivery time of control codes. Control codes' priorities are considered in this model as well. In this article we analyze the case when the network should be fault tolerant to a given number faults in nodes and links. We do not consider errors' occurrence when time-codes, interrupt and acknowledge codes generating.