A method for a slave bus and a master bus includes receiving a first frame via a first data channel, wherein the first frame includes at least first header data, first payload data and first checksum. The method further includes implementing a function depending on the header data contained in the received first frame, and generating a second frame including second header data, second payload data, which are determined by the implemented function, and a second checksum. The second checksum is ascertained at least on the basis of the second payload data and the first header data contained in the received first frame. The method also includes transmitting the second frame via a second data channel simultaneously with receiving the first frame via the first data channel.

A crossbar switch comprises two or more data inputs 10, two or more data outputs 100, a buffer 30 between the inputs and the outputs, an arbiter 52 associated with each output and configured to select data from one of the inputs when there is contention at the output, a bypass 32 associated with the buffer so that the buffer can be enabled or disabled, and a buffer controller 60 configured to enable or disable the buffer. The buffer controller further includes an accumulator 70 configured to assess whether a time-based average of the contention rate, or an average injection rate, at the output associated with the buffer, has reached a predetermined threshold. This prevents the buffer being enabled when the contention is only intermittent, which reduces power consumption without significant loss of performance.

Method and apparatus for implementing an optimized credit return mechanism for packet sends. A Programmed Input/Output (PIO) send memory is partitioned into a plurality of send contexts, each comprising a memory buffer including a plurality of send blocks configured to store packet data. A storage scheme using FIFO semantics is implemented with each send block associated with a respective FIFO slot. In response to receiving packet data written to the send blocks and detecting the data in those send blocks has egressed from a send context, corresponding freed FIFO slots are detected, and a lowest slot for which credit return indicia has not be returned is determined. The highest slot in a sequence of freed slots from the lowest slot is then determined, and corresponding credit return indicia is returned. In one embodiment an absolute credit return count is implemented for each send context, with an associated absolute credit sent count tracked via software that writes to the PIO send memory, with the two absolute credit counts used for flow control.

Techniques are disclosed relating to arbitration among register file accesses. In some embodiments, an apparatus includes a register file configured to store operands for multiple client circuits and arbitration circuitry configured to select from among multiple received requests to access the register file. In some embodiments, the apparatus includes first interface circuitry configured to provide access requests from a first client circuit to the arbitration circuitry and supplemental interface circuitry configured to receive unsuccessful requests from the first client circuit and provide the received unsuccessful requests to the arbitration circuitry. The supplemental interface circuitry may provide additional catch-up bandwidth to clients that lose arbitration, which may result in fairness during bandwidth shortages.

Techniques are disclosed relating to arbitration among register file accesses. In some embodiments, an apparatus includes a register file configured to store operands for multiple client circuits and arbitration circuitry configured to select from among multiple received requests to access the register file. In some embodiments, the apparatus includes first interface circuitry configured to provide access requests from a first client circuit to the arbitration circuitry and supplemental interface circuitry configured to receive unsuccessful requests from the first client circuit and provide the received unsuccessful requests to the arbitration circuitry. The supplemental interface circuitry may provide additional catch-up bandwidth to clients that lose arbitration, which may result in fairness during bandwidth shortages.

A method for bandwidth allocation includes receiving requests for bus channel access from two or more master devices. Next, the method selects one of priority-based allocation or credit-based allocation. Upon selecting the priority-based allocation, the method grants bus channel access based on pre-assigned priorities for bus channel access. Upon selecting credit-based allocation, the method grants bus channel access based on pre-allocated credits for bus channel access, and the method decrements the credit from the master device that has been granted bus channel access.

A device includes a first and a second stage round robin arbitrations. The first stage receives request signals and selects a subset the request signals. Each request signal is associated with whether a component is requesting access to a common resource. The second stage receives the selected subset and grants access to the common resource to each request signal of the selected subset that is requesting access, in a round robin fashion. The second stage outputs an enable signal to the first stage when the selected subset is processed. The first stage selects another subset and transmits the selected another subset to the second stage for round robin processing thereof. The process is repeated until all subsets with at least one request signal to access the common resource is processed and granted access in a round robin fashion.

A memory request management system may include a memory device and a memory controller. The memory controller may include a read queue, a write queue, an arbitration circuit, a read credit allocation circuit, and a write credit allocation circuit. The read queue and write queue may store corresponding requests from request streams. The arbitration circuit may send requests from the read queue and write queue to the memory device based on locations of addresses indicated by the requests. The read credit allocation circuit may send an indication of an available read credit to a request stream in response to a read request from the request stream being sent from the read queue to the memory device. The write credit allocation circuit may send an indication of an available write credit to a request stream in response to a write request from the request stream being stored at the write queue.

A memory request management system may include a memory device and a memory controller. The memory controller may include a read queue, a write queue, an arbitration circuit, a read credit allocation circuit, and a write credit allocation circuit. The read queue and write queue may store corresponding requests from request streams. The arbitration circuit may send requests from the read queue and write queue to the memory device based on locations of addresses indicated by the requests. The read credit allocation circuit may send an indication of an available read credit to a request stream in response to a read request from the request stream being sent from the read queue to the memory device. The write credit allocation circuit may send an indication of an available write credit to a request stream in response to a write request from the request stream being stored at the write queue.

Systems, methods, and apparatus for data communication are provided. A method performed by a bus master includes terminating transmission of a first datagram by signaling a first bus park cycle on a serial bus, causing a driver to enter a high-impedance state, opening an interrupt window by providing a first edge in a clock signal transmitted on a second line of the serial bus, closing the interrupt window by providing a second edge in the clock signal, signaling a second bus park cycle on the serial bus, initiating an arbitration process when an interrupt was received on the first line of the serial bus while the interrupt window was open, and initiating a transmission of a second datagram when an interrupt was not received on the first line of the serial bus while the interrupt window was open.