Specification and Implementation of the Universal Time Coordinated Synchronization Unit (UTCSU)

High-accuracy external clock synchronization can only be achieved with adequate hardware support. We analyze the requirements and present the specification and implementation of an ASIC running under the acronym UTCSU dedicated to that purpose. It is built around an elaborated local clock, which is based on an adder driven by a fixed-frequency oscillator. This novel clock design allows a fine grained rate adjustability apt for maintaining both local time with linear continuous amortization and accuracy information as needed in interval-based clock synchronization. Additional features incorporated in our UTCSU are facilities to timestamp clock synchronization data packets, interfaces to couple GPS receivers, some application support as well as sophisticated self-test machinery. Apart from addressing design and engineering issues of the chip, we also provide a basic programming model.