System-Level Access to On-Chip Instruments

Modern integrated circuits (ICs) contain thousands of instruments to enable testing, tuning, monitoring, and so on. These on-chip instruments must be accessed through the ICs' life-time. However, when ICs are mounted on Printed Circuit Boards (PCBs), access from system-level is challenged due to complex system hierarchies with a multitude of interfaces. In this paper we enable access from system-level to chip-level instruments by proposing hardware, protocol, and communication schemes. We have validated our scheme by implementing a system with two ICs on a Field-Programmable Gate Array (FPGA) where each IC includes an IEEE Std. 1687 network, communication between ICs is with Serial Peripheral Interface (SPI) and communication with the outside is with Universal Asynchronous Receiver Transmitter (UART). In experiments we evaluate communication based on software (polling) and hardware (interrupt) as well as overhead in terms of transported data and needed area.