Abstract: A self-contained DAC that is especially suitable for use as an IP core, particularly for SOC (System on Chip) implementation. Techniques are applied to employ certain circuits (such as arithmetic element 302) to perform multiple functions in the DAC, thereby resulting in space saving. Techniques are also applied to employ fewer circuits per functional block to achieve further space saving. By employing multiple clock domains and turning on selective circuits on an as-needed basis, power saving is also realized.

Abstract: A self-contained DAC that is especially suitable for use as an IP core, particularly for SOC (System on Chip) implementation. Techniques are applied to employ certain circuits (such as arithmetic element 302) to perform multiple functions in the DAC, thereby resulting in space saving. Techniques are also applied to employ fewer circuits per functional block to achieve further space saving. By employing multiple clock domains and turning on selective circuits on an as-needed basis, power saving is also realized.

Abstract: A system includes a requesting agent coupled to a system bus. The system bus includes an address bus, control lines for indicating a requested transfer type, a data bus, address bus arbitration control lines and data bus arbitration control lines. The system further includes a system bus arbiter coupled to the system bus for resolving competing requests for access to the address bus and for separately resolving competing requests for access to the data bus. A graphics controller for enabling the requesting agent to access a frame buffer has a memory, which may be a FIFO, responsive to a first control signal, for storing data received from a frame buffer. The memory is further responsive to a second control signal for supplying the stored data to the data bus. The graphics controller also includes a controller coupled to the system bus and to the memory means.

Abstract: A direct memory access (DMA) controller is connected to the CPU bus of a computer system through a bus interface and is also connected to an I/O bus, which is coupled to one or more I/O controllers. Multiple channels, each corresponding to a particular I/O controller, are contained within the DMA controller. The DMA controller controls DMA transfers between the I/O controllers and the main memory of the system and allows multiple transfers to occur concurrently. The DMA controller controls transfers in part through a first arbiter which arbitrates requests for access to the CPU bus coming from the DMA channels and a second arbiter which arbitrates requests for access to the I/O bus coming from the DMA channels and the CPU.

Abstract: An ethernet receive channel, corresponding to an ethernet controller, is contained within a direct memory access (DMA) controller. The DMA controller is connected to the CPU bus of a computer system through a bus interface and is also connected to an I/O bus, which is coupled to one or more I/O controllers, including an ethernet controller. The ethernet receive channel contains a buffer and multiple register sets storing the number of packets to be received for a particular DMA transfer, the address where the next byte of the incoming ethernet packet will be written in memory, and control information for the transfer. The address registers are initially programmed with the starting location for the transfer in main memory, which correspond to segments within chains of contiguous physical memory. During a transfer, the address registers are updated to contain the location where the next portion of the incoming ethernet packet will be written in memory.

Abstract: In a computer system an apparatus interconnects a first bus, a second bus and a frame buffer, wherein the first bus and the second bus are of incompatible bus architecture types. For example the first bus may be a loosely coupled bus having split-bus transaction capability, such as the ARBus, and the second bus may be a tightly ordered bus, such as the PCI local bus. The apparatus includes bridge hardware for converting access requests from the first bus into suitable requests for the second bus. Data paths within the apparatus allow data to be routed from one bus to another. The apparatus further includes a frame buffer controller that is accessible from either of the first or second buses for performing read or write operations from/to the frame buffer. Data path logic allows data to be routed from any of the first bus, second bus and frame buffer to any other one of these three locations.

Abstract: A method of prioritizing computer resource access requests to a shared computer resource, such as a video frame buffer, includes the steps of providing a number, n, of priority schemes in correspondence with a like number of potentially requesting entities, where n is an integer greater than one, and where each priority scheme designates relative priority of the potentially requesting entities with respect to one another. Thus, for each priority scheme there exists one corresponding potentially requesting entity, and a number, n-1, of noncorresponding potentially requesting entities. Next, one of the priority schemes is selected for use as a current priority scheme. A set of currently requesting entities is then determined from the number of potentially requesting entities, and the current priority scheme is used to select a highest priority requesting entity from the set of currently requesting entities.

Abstract: A direct memory access (DMA) controller is connected with the CPU bus of a computer system through a bus interface and also to an I/O bus, which is connectable to one or more I/O controllers. The DMA controller contains multiple channels, each corresponding to a particular I/O controller, which are coupled to both the bus interface and the I/O bus. Each of the channels contains at least one register set storing information for the transfer and a data buffer holding the data during a transfer between the I/O bus and the CPU bus.

Abstract: An apparatus for transforming pixel data from a data bus into an expected format for storage in a frame buffer has a first multiplexor, a second multiplexor and a controller. The first multiplexor includes two data inputs coupled to the data bus so that the first data input provides pass-through of received data, and the second data input provides end-for-end byte swapping of bus data. Input selection is made by a byte-swap control signal. The second multiplexor includes an output and four data inputs. The output of the first multiplexor is coupled to each of the four inputs of the second multiplexor so as to provide for end-for-end byte swapping from two of the inputs, end-for-end word swapping from another one of the inputs, and end-for-end half-word swapping from a fourth input. The second multiplexor is responsive to a reorder control signal that alternatively selects one of the first, second, third and fourth inputs of the second multiplexor to be gated to the output of the second multiplexor.

Abstract: A computer bus bridge interconnects first and second buses, the first bus being big-endian and the second bus being little-endian. First address and size signals received from the first bus during a first bus cycle are converted into second address and data unit enable signals for transmission on the second bus during a second bus cycle. The first address comprises a low-order address portion and a remaining upper-order address portion. The data unit enable signals are generated from the low-order address portion and the size signals of the first bus. An address offset is generated from the data unit enable signals. The remaining upper-order address portion of the first address are then concatenated with the address offset and a predetermined lower address portion for use as the second address. The data unit enable signals may designate, say, up to 4 possible data bytes being transferred during a single beat on the second bus.

Abstract: A system has a system resource, such as a frame buffer, coupled to a system bus, the system bus conveying a request for access to the system resource from another system element connected to the system bus. An apparatus for presenting the access request to the system resource from the system bus includes a queue, a multiplexor that is preferably glitchless, and a controller. The queue has an input for receiving access request information from the system bus; one or more storage elements, each for storing access request information, wherein the one or more storage means are connected to form a queue having a head and a tail; and a queue output for supplying data stored in the head of the queue. The multiplexor has a first input coupled to the queue output, a second input for receiving the access request information from the system bus, and a multiplexor output for supplying the access request to the system resource.

Abstract: An FDDI system and method for transmitting to an optical medium, upon receipt of token, frames of synchronous data and frames of asynchronous data having different levels of priority. The network on which the FDDI is implemented includes a plurality of processors each having a system for storing the frames of data in queues corresponding to priority, and an output buffer configured to have a plurality of logical FIFOs corresponding to the queues. Data is transferred one queue at a time from the system memory to the output buffer through a single physical FIFO. To prevent the FIFO from "locking-up" as a result of any residual data remaining therein following each transfer of a frame to the output buffer, storage remaining available for a particular queue of the output buffer to be transmitted to the medium is detected. Data is transferred from the system memory to the FIFO memory only if the storage remaining available is at least equal to the storage capacity of the FIFO memory.

Abstract: Method of detecting the INFO 1 signal pattern which avoids false activation of a data transmission line caused by noise on the line. An initial line sampling rate four times the nominal 192 kbs line rate is used to detect a HIGH mark to avoid the difficulties resulting from sampling right at the edge of a mark. Subsequent sampling is done at the nominal line rate to detect two opposite polarity marks out of every consecutive eight-bit time periods. If six consecutive eight-bit time periods are detected, each having its HIGH and LOW marks in the same relative positions, the line is activated. The method is readily implemented as a set of three "state machines" and consequently can be constructed from programmable logic arrays.