Abstract: Embodiments of the present invention relate to a mechanism to prevent the oscillator from being stopped when a host development system is coupled to the background debug communications interface and the background debug mode has been enabled. This allows background debugging operations to continue when the target data processing system is in a low power mode. Other embodiments relate to a mechanism for allowing a host development system to request a synchronization timing pulse from a target data processing system so the correct clock speed can be determined for background communications. Alternate embodiments relate to a data processing system having a system clock unit and a background debug system where the background debug system includes a background debug clock unit, separate from the system clock unit, and an enable control. When the enable control is asserted, the background debug clock unit is enabled, independent of the system clock unit.

Abstract: A memory circuit includes a memory structure having sets of redundant columns where each set of redundant columns can replace a column of the memory array that may include a defective cell. Selection of the redundant columns for a memory access is accomplished by performing an address comparison between the address provided to the memory and one or more predetermined values that indicate which portion of the data array each set of redundant columns replaces. Based on this address comparison, a column redundancy select signal is asserted when a set of redundant columns is selected. For a read operation, the column redundancy select signal propagates through redundant column logic select the appropriate data from a particular set of redundant columns. This redundant data that is selected is substituted for data stored in the memory array for the read operation.