This paper proposes a test coprocessor for a 32-bit MicroBlaze CPU core. A microprogrammed architecture is used to implement the coprocessor control path, offering a flexible solution that ensures a straightforward expansion of the test command set. The current version supports a set of SVF-like commands that is able to control one built-in IEEE 1149.1 boundary-scan infrastructure. The proposed test coprocessor is useful in a wide range of online test applications, and namely in the case of mission-critical embedded systems, where online fault detection and diagnosis become particularly important.

This paper describes a microprogrammed architecture for an embedded coprocessor that is able to control IEEE 1149.1 to IEEE 1149.7 test infrastructures, and explains how to expand the supported test command set. The coprocessor uses a fast simplex link (FSL) channel to interface a 32-bit MicroBlaze CPU, but it can work with any microprocessor core that accepts this simple FIFO-based interface method. The implementation cost (logic resource usage for a Xilinx Spartan-6 FPGA) and the performance data (operating frequency) are presented for a test command set comprising two parts: 1) the full IEEE 1149.1 structural test operations; 2) a subset of IEEE 1149.7 operations selected to illustrate the implementation of advanced scan formats.