Abstract: A clock circuit with a plurality of inputs for a plurality of respective clock signals, the clock signals alternating between a first and a second state. At least one divider circuit is arranged to take an input clock signal and provide an output that is in the first state for a first fixed multiple of the duration the clock signal is in the first state, and in the second state for a second fixed multiple of the duration the clock signal is in the second state. A plurality of delay circuits are arranged to take the output of the divider circuit or circuits and provide a set of outputs each delayed by a fixed duration. A selection circuit is arranged to select the outputs of the delay circuits in sequence. The selection circuit is arranged to select the next output in the sequence at or after the time when the selected output changes from the first state to the second state.

Abstract: System and method are implemented to allow phase lock loop (PLL) status testing during a Serializer/Deserializer (SERDES) internal loopback built-in self-test (BIST). An existing pseudo random binary sequence (PRBS) data generator is modified to include a mode that produces a data pattern having a frequency content low enough to be verified on the tester used at the probe.

Abstract: There is provided a Clock recovery apparatus comprising: an early/late voter for deciding whether a current sampling point needs to be advanced or retarded, wherein said early/late voter passes an Up/Down signal to an interpolator for maintaining a clock signal; a frequency accumulator and rate multiplier 30 for generating further signals which are summed with those of the Up/Down signal of the early/late voter to provide an improved control signal to the phase interpolator. The accumulator is responsive to frequency changes in the input signal, and said interpolator acts on said Up/Down signals to adjust the clock signal by stepping it forward or backward according to control need, so that said sampling point can be advanced or retarded.

Abstract: System and method are implemented to allow phase lock loop (PLL) status testing during a Serializer/Deserializer (SERDES) internal loopback built-in self-test (BIST). An existing pseudo random binary sequence (PRBS) data generator is modified to include a mode that produces a data pattern having a frequency content low enough to be verified on the tester used at the probe.

Abstract: The use of daughterboards connecting to a motherboard in an emulation system allows for the upgrading of the emulation field programmable gate arrays in the system, and for the use of different types of field programmable gate arrays. These changes can be made without changing the motherboard. The motherboard has sockets which have pin locations which are allocated to interconnect structures and to an emulation bus. The chips on the cards can contain different emulation field programmable gate arrays, or could contain core chips, which can be directly connected to the motherboard through the daughterboards. The daughterboards connect the emulation FPGAs and the core chips to the correct pin locations of the sockets. Controller chips on the cards allow for different types of field programmable gate arrays to be used and simplify the configuration loading and debugging of the system. Additionally, the present system includes a system using a reconfigurable interface in a controller chip.