Abstract: A system and method checks whether messages exchanged between first and second modules are being lost or gained. The first module has a request counter and a capture register. The second module has a request accumulator and a capture register. As the first module issues and receives messages, it increments and decrements its request counter. As the second module receives and issues messages, it increments and decrements its request accumulator. To check for lost or gained messages, the first module copies the current value of its request counter into its capture register, and issues a marker to the second module. The first module decrements its capture register in response to receiving post-marker messages, but does not increment its capture register. Upon receipt of the marker, the second module copies the current value of its request accumulator into its capture register, and returns the marker to the first module. When the first module receives the marker, it stops decrementing its capture register.

Abstract: A method and apparatus for queue selection is described below as Prioritized Continuous-Deficit Round Robin (PC-DRR) Scheduling. In PC-DRR scheduling a queue is selected as a source for the shared datapath using a modified round-robin approach, where queues are cyclically, sequentially evaluated to determine whether or not there is data stored in the queue. In PC-DRR scheduling, each queue is assigned a weight, wherein the weight corresponds to a predefined bandwidth that is allocated to the queue. Thus, the weight defines a fixed allotment of transmit opportunities that are to be allowed for the associated queue during its transmit tenure. In a preferred embodiment, a minimum permissible weight that is assigned to a queue is equal to a Maximum Packet Size. As data are drained from the queue, the weight is decreased incrementally by the amount of data sent, providing a balance.

Abstract: The input bandwidth of a data transfer device is increased by altering the conventional memory arbitration method in which a data cell is stored and a data cell is forwarded during each data transfer cycle. The input data rate is monitored and when the input data rate exceeds the maximum average throughput of the memory, the outcome of the memory arbitration cycle is changed so that the memory arbitration cycle consists of two stores (memory write operations) instead of one store and one forward (memory read operation.) In effect, the input memory arbitration process steals cycles from the output memory arbitration process when the input load exceeds that of the maximum average memory throughput. In accordance with one embodiment, the input data rate is monitored by examining input port FIFO buffers for the presence of data cells waiting for storage.

Abstract: A data coding method for digital communication systems is disclosed. In two embodiments, every four bits of data in a first data channel are mapped to a five bit code symbol. The five bit code symbols are chosen to have a duty cycle of 40 to 60 percent. In the first embodiment, a second channel of data is optionally interleaved with the encoded first channel data by placing single bits from the second channel every sixth bit in the data stream between each five bit code symbol. A plurality of synchronizing words are each formed from other pairs of five bit code symbols, and, in the two channel embodiment, the optional two bits of data from the second channel. The synchronizing words also have a duty cycle of 40 to 60 percent, and further have the characteristic that their bit patterns can only occur where they are placed in a stream of encoded data.

Abstract: A method for scrambling and descrambling television programs in which the horizontal synchronizing information is suppressed at a CATV supplier's head-end and then regenerated at the subscriber's converter. The pulse frequency is multiplied by a factor N/M, in which N and M are integers thereby generating a synthesized pulse stream which is, in turn, encoded with data identifying the values for N and M. This encoded pulse stream is modulated onto the audio subcarrier wave in the TV video signal and transmitted to the converter. The converter then demodulates and recovers the encoded pulse stream, decodes the same to recover the identifying data, using this data to obtain the correct values for N and M which have been transmitted separately on a digital data channel. The converter then multiplies the synthesized pulse stream by M/N regenerating the horizontal synchronizing pulse stream and inserts the same into the TV video signal at the proper phase.

Abstract: A programmable time-of-use metering system is disclosed for metering electrical energy consumption at multiple rates depending on the time of day, time of week and time of year in which the energy is being consumed. A method for registering total energy consumed by a metered system as well as energy consumed during preselected time intervals is also disclosed.