Apparatus and method for clock signal synchronization in JTAG testing in systems having selectable modules processing data signals at different rates

摘要

In a test and debug system in which a plurality of selectable modules under test have different operational rates, a selection unit associated with each module is used to control the application of the RCLK signal from the module to the combiner unit, the combiner unit providing a composite RCLK signal. Each selection unit has output signals of RCLK_NE and RCLK_PE signals which are applied to an combiner unit to form the composite RCLK signal. In response to the SELECT signal, the RCLK_NE and RCLK_PE are synchronized with the module RCLK signal. When the SELECT signal is removed, the RCLK_NE and RCLK_PE signals are continuously applied to the combiner unit.