摘要:
A transceiver (5) for an asymmetric communication system such as asymmetric digital subscriber line (ADSL) includes a configuration register (71) defining operation at either a central office (CO) or a remote terminal (RT). The configuration register (71) includes a control bit (72) for selecting either CO or RT mode. The transceiver (5) includes a signal processing module (70) configured according to the state of the control bit (72). For example, a digital interface (70) converts transmit data into transmit symbols and converts received symbols into receive data. The digital interface (70) uses a large memory (158) as a buffer in the transmit path and a small memory (160) as a buffer in the receive path in CO mode. In RT mode, the digital interface (70) uses the small memory (160) in the transmit path and the large memory (158) in the receive path. The selective configuration allows a single integrated circuit to be used in both CO and RT equipment.
摘要:
A bandgap reference circuit providing a continuous output reference voltage. The bandgap reference circuit comprises an operational amplifier, an output circuit, and a compensation circuit. The operational amplifier receives a first input signal and a second input signal and provides an output signal in response to a difference in voltage between the first input signal and the second input signal. The output circuit receives the output of the operational amplifier and provides an output reference voltage. The output circuit provides the first input signal and the second input signal to the operational amplifier in such a way as to maintain the output reference voltage at a substantially constant value. The compensation circuit provides a current to the output circuit to compensate for currents conducted from the bases of transistors in an input stage of the operational amplifier, thereby making the output reference voltage more stable.
摘要:
A data stream to be transmitted is received by a digital interface (52) and converted into a frequency encoded data. A gains block (54) receives the frequency encoded data and a gain adjustment signal, and produces a gain adjusted data to compensate for undesirable system level passband gain variation. The gain adjusted data is converted to a time domain data. The time domain data is processed by a high-pass and a droop correction filter (58, 59) to produce a filtered data. The filtered data is provided through an analog front-end (60) in order to provide a filtered analog data.
摘要:
A cascaded integrator-comb (CIC) interpolation filter is included within a digital-to-analog converter (138) and includes two up-samplers (150, 164). The two up-samplers (150, 164) also include a sample-and-hold function. The first up-sampler (150) up-samples an output of a differentiator (140). The second up-sampler (164) up-samples an output of an integrator (152) This reduces the area and power requirements of the CIC interpolation filter, while providing approximately the same filtering performance in the pass band and transition band. The total over-sample ratio of the CIC interpolation filter is equal to the first up-sampling ratio multiplied by the second up-sampling ratio. The stop band requirements of the CIC interpolation filter determines the relative sizes of the first and second up-sampling ratios.
摘要:
A memory (10) has a plurality of memory cells, a serial address port (47) for receiving a low voltage high frequency differential address signal, and a serial input/output data port (52, 54) for receiving a high frequency low voltage differential data signal. The memory (10) can operate in one of two different modes, a normal mode and a cache line mode. In cache line mode, the memory can access an entire cache line from a single address. A fully hidden refresh mode allows for timely refresh operations while operating in cache line mode. Data is stored in the memory array (14) by interleaving in multiple sub-arrays (15, 17). During a hidden refresh mode of operation, one sub-array (15) is accessed while another sub-array (17) is refreshed. Two or more of the memories (10) may be chained together to provide a high speed low power memory system.
摘要:
A method and circuit includes providing at least one conductor for receiving an input signal. A termination circuit and a clamp circuit are coupled to the at least one conductor. The termination circuit is enabled while the clamp circuit remains enabled. The clamp circuit is disabled. After disabling the clamp circuit, while the termination circuit remains enabled, both a first differential comparator and a second differential comparator are enabled. The first differential comparator receives a first differential input signal at a first input and a second differential input signal at a second input. The second differential comparator detects when a difference between the first differential input signal and the second differential input signal is greater than a predetermined value and enables transfer of an output of the first differential comparator to a memory controller.
摘要:
A memory (10) has a plurality of memory cells, a transceiver (56) for receiving a low voltage high frequency differential address signal, and a serial input/output data port (52, 54) for receiving a high frequency low voltage differential data signal. The memory (10) can operate in one of two different modes, a normal mode and a cache line mode. In cache line mode, the memory can access an entire cache line from a single address. A fully hidden refresh mode allows for timely refresh operations while operating in cache line mode. Data is scored in the memory array (14) by interleaving in multiple sub-arrays (15, 17). During a hidden refresh mode of operation, one sub-array (15) is accessed while another sub-array (17) is refreshed. Two or more of the memories (10) may be chained together to provide a high speed low power memory system.
摘要:
A dual tone detector (100) for a single dual tone, a dual tone multi-frequency (DTMF), or similar system processes an input signal through both bandpass (103) and band reject (104) tone detectors. If both the bandpass (103) and band reject (104) tone detectors detect a tone, then the dual tone detector (100) provides a tone detect output signal. If only the bandpass tone detector (103), which is susceptible to false tones, detects a tone, then a voice input signal is muted and the tone detector (100) activates the tone detect output signal only if both the bandpass (103) and band reject (104) tone detectors subsequently detect a tone. In one embodiment, a dual bandpass/band reject tone detector (120) processes the input signal through shared front-end band reject filters (121, 122), limiters (124), resonators (127, 128), and a processing section (130) in order to save circuit area. Limiter and peak detector functions are also implemented in shared circuitry to further reduce circuit area.
摘要:
An analog two pole filter is provided which uses a single amplifier to implement a predetermined transfer function. The filter has a differential input and converts the two inputs to a single output utilizing the same amplifier which performs the filtering function. By coupling a capacitor across the differential input and utilizing the differential aspect of the input signals, the capacitor may be implemented with half the capacitance otherwise required to implement the predetermined transfer function, thereby minimizing circuit area.
摘要:
Hashing and pattern matching are used in an information processing system to process incoming messages from a network such as an Ethernet-based network. Using hashing and pattern matching increases the efficiency of message acceptance and rejection without increasing software-based processor tasks. A hash function and a pattern matching function are performed on a message received by an information processing system, and the message is selectively accepted based on at least one of a hash result and a pattern matching result. The incoming message can be searched for the existence of patterns and the absence of the patterns. The incoming message can be searched for the existence of multiple patterns. The results of pattern matching can be used not only for acceptance and rejection of messages, but also for other post-receipt tasks such as selective storage of incoming messages according to identified relative priorities or absolute criticality of messages having particular pattern matches.