Abstract: An arrangement, system, and method to allow a computer system to have a normal operating mode with full display capability and a low-power operating mode with reduced display capability is provided. The computer system automatically switches to the low-power operating mode from the normal operating mode following a programmable period of inactivity. While display data is retrieved from an external DRAM in the normal operating mode, display data is retrieved from an internal SRAM in the low-power operating mode. The computer system switches back to the normal operating mode when one of the predetermined activities is detected.

Abstract: A network controller, which allows data frames received to be held in an internal memory buffer, has the capability to selectively switch between a DMA mode of data transfer and a non-DMA mode of data transfer to move data frames from the internal memory buffer to a desired location. When the overflow of the memory buffer is anticipated, a DMA controller is automatically engaged to move the data frames to a system memory to prevent the received frames from being discarded. An auto-DMA decision logic engages the DMA controller based on factors such as the number of data frames accumulated in the memory buffer, remaining capacity of the memory buffer, frame loading and unloading rates, and time interval during which data frames have been received without completely unloading the memory buffer.

Abstract: The present invention pertains to a detection and switching circuit for processing and then routing signals between various devices (e.g., modem, telephone, speaker-phone, external or on-board speakers, microphone, etc.) coupled to a computer system. First, a user plugs the desired devices to the computer system. Next, the user selects amongst several different modes of operation. The circuit monitors the status of these various devices and the status of the incoming signals on the phone line. The resident software then processes the signals (e.g., analog audio signals or digital data signals) into the particular formats corresponding to these particular devices. Finally, the switches are set to route the signals to the appropriate devices. The processing and switching steps are performed automatically in accordance with the particular mode that the user has selected.

Abstract: A periodic training signal is transmitted over a communications channel from a transmitter to a receiver. At the receiver, a spectrum estimation module is used to measure the spectrum of a set of uncorrected samples of the periodic training signal. The spectrum estimate is available at a discrete frequency spacing of an integer fraction (L>1) of the frequency spacing of the set of samples of the periodic training signal. A timing offset estimation module is then used to measure the ppm offset between the local and remote crystals. The timing offset estimation module runs in parallel with the spectrum estimation module. The spectrum estimate is convolved with the DFT of a periodic ramp function and the result squared to product an error spectrum. The error spectrum represents the error induced by differences between timing in the transmitter and receiver clock. The error spectrum is subtracted from the estimated spectrum to produce a corrected spectrum.

Abstract: A wired combinational logic arrangement responsive to N binary signal sources includes N circuits, one for each source. The circuits drive a common output terminal. Each circuit includes first and second devices for pulling the common terminal to first and second different voltages during successive abutting activation periods. The first device supplies a current to the common terminal that is considerably greater than the current supplied to the common terminal by the second device. The arrangement further includes a third device for pulling the common terminal to the second voltage at all times. The third device supplies a current to the common terminal that is either equal to or less than the current supplied by the second device.

Abstract: An apparatus and method for canceling system oscillations caused by acoustical coupling is provided. The invention can be implemented in a low voltage environment and as an integrated circuit. Audio voltage signals generated by a microphone are provided as input to a data/fax/voice modem. The data/fax/voice modem processes the audio voltage signals and outputs differential transmit voltage signals to a hybrid/daa circuit for converting to a two-wire (tip and ring) circuit before connecting to a communication device such as a land based telephone or a cellular radio. Audio voltage signals generated by the communication device are provided via a two-wire (tip and ring) circuit to the hybrid/daa circuit for converting into a four-wire circuit and then provided as input to the data/fax/voice modem as differential receive voltage signals.

Abstract: This invention provides efficient and flexible data transfer management for a First-In First-Out (FIFO) buffer connects to a system bus and implements multiple data thresholds (e.g., two). Data transfer by the FIFO is controlled by either casually or more aggressively acquiring the system bus based on the amount of data inside the FIFO and on the state of the system bus. By balancing the bus activity level against the FIFO data level, bus access is facilitated at times when the bus has lower activity. This makes the FIFO less obtrusive when moving data across the bus. As a result, the bus is used more efficiently. The system bus is casually acquired when the FIFO data level reaches a soft threshold and the system bus is idle. Casual control of the system bus is relinquished when request from another device sharing the bus is received and a predetermined amount of data has been transferred. On the other hand, the system bus is more aggressively acquired when the FIFO data level reaches a hard threshold.

Abstract: A data communication circuit of a computer system, includes transmitter and receiver circuits each having first and second data paths for respectively communicating synchronously and asynchronously formatted data on an alternatively selected basis, and a control circuit for controlling such communications. Included in the first data paths of the transmitter and receiver circuits are certain field check generating or error checking circuitry which are switchably coupled by their respective control circuits to their corresponding second data paths when synchronously formatted data is being asynchronously communicated through the second data paths.

Abstract: An apparatus and method for efficiently receiving a long string of short data packets. Storing a long string of short data packets received from external devices can be inefficient in terms of system resources such as system memory and CPU time. In the preferred embodiment of the present invention, both the number of data packets in the FIFO buffer and the demand of system memory are monitored. A FIFO buffer of at least 32 bytes deep and having a packet-based threshold is implemented to monitor the number of data packets in the FIFO buffer. When the number of data packets in the FIFO buffer is equal to or exceeds the threshold and there is a predetermined number of free buffer memory available, data is transferred from the FIFO buffer to system memory. The number of data packets transferred from the FIFO buffer is also monitored to control the amount of data transfer. Any data stuck inside the FIFO buffer for a predetermined period of time is automatically unloaded.

Abstract: A pipelined alignment shifter allows transfer of strings of bytes between memories which are non-aligned in computer systems or serial communications and networking with the memories arranged in N fields of B bits, where N and B are integers. The shifter has B copies of N-1 storage elements connected to N copies of N to 1 (N:1) multiplexers. An enable signal E is commonly transmitted to each copy of N-1 storage elements to cause each N-1 storage element, e.g., a latch or a register, to output a previously stored input and to store a corresponding input. A selection signal S indicative of the offset difference between the memories is commonly transmitted to each copy of N:1 multiplexer for realignment of non-aligned boundaries in data transfer mechanisms such as Direct Memory Access (DMA) controllers.

Abstract: An apparatus and method for acquiring address and command information related to a synchronous bus transaction with at most zero hold-time over substantially the duration of the bus transaction. Due to state changes, bus transaction address and command information may become invalid over the duration of the bus transaction. A transparent latch circuit is used to make the information available as soon as the information is received and to acquire valid information related to the bus transaction before a rising clock edge of the next clock cycle following a bus transaction request. A synchronous flip-flop circuit is utilized simultaneously to capture alternate valid information related to a bus transaction having at most zero hold-time. The acquired valid information and the alternately acquired valid information ensure that stable and valid bus transaction information are available over substantially the duration of the transaction. Moreover, by decoding the information as soon as they are received (i.e.

Abstract: An apparatus and method for acquiring data information provided by a synchronous bus transaction with at most zero hold-time. A transparent latch circuit is used to capture bus transaction information before a rising clock edge of the next clock cycle following a bus transaction request and a data phase starting signal thereby meeting the zero-hold requirement. At the same time, bus transaction information is decoded to determine whether the current phase is a data phase, data information is present in the current bus transaction, memory addresses presented are within an allowable range, and bus transaction command is of the type recognized. If all the above conditions are met, the information captured by the transparent latch circuit is registered by a synchronous flip-flop circuit as valid data information.

Abstract: A method and arrangement for adjusting a clock frequency to allow computer devices with different clock frequencies to operate together. The arrangement scales the input clock frequency to be scaled by any desired fraction by controlling both the numerator and denominator of the scaling fraction. Clock frequency adjustment is achieved by transforming the input clock frequency into a periodic clock frequency that is reset following a desired clock period and scaling this periodic clock frequency according to a desired divisor value to generate the desired clock frequency.

Abstract: A sense amplifier circuit includes a voltage developing stage which receives first and second data inputs, din1 and din2, and generates a differential voltage, in response to feedback signals received from a first and second data outputs, dout1 and dour2, of the sense amplifier circuit, which is indicative of a voltage difference between the first and second data inputs, din1 and din2; a full-swing locking stage which generates and latches, in response to a control signal .PHI..sub.2 ', complementary latched data outputs from the first and second data outputs, dout1 and dout2, generated by the voltage developing stage; and a voltage equalization stage which equalizes, in response to a control signal .PHI..sub.0 ', voltages on data lines respectively connected to the first and second data outputs, dout1 and dout2. In addition, the voltage equalization stage is used to initiate the voltage developing stage. Timing of the control signals, .PHI..sub.0 ' and .PHI..sub.2 ', is such that the control signal .PHI..