Abstract: A multi-queue FIFO memory device that uses existing pins of the device to load a desired number of queues (N) into a queue number register is provided. The queue number register is coupled to a queue size look-up table (LUT), which provides a queue size value in response to the contents of the queue number register. The queue size value indicates the amount of memory (e.g., the number of memory blocks) to be included in each of the N queues. The queue size value is provided to a queue start/end address generator, which automatically generates the start and end address associated with each queue in response to the queue size value. These start and end addresses are stored in queue address register files, which enable proper memory read/write and flag counter operations.

Abstract: A serial buffer having a plurality of virtual queues, which can be allocated to include various combinations of on-chip dual-port memory blocks, on-chip internal memory blocks and/or off-chip external memory blocks. The virtual queues are allocated and accessed in response to configuration bits and size bits stored on the serial buffer. Relatively large external memory blocks can be allocated to virtual queues used for data intensive operations, while relatively small and fast dual-port memory blocks can advantageously be allocated to virtual queues used for passing command and status information. The serial buffer provides an efficient and flexible manner for utilizing available memory, which not only minimizes the access latency but also provides a large amount of buffer space to meet different application needs.

Abstract: A method of operating a multi-queue device, including: (1) storing a plurality of read (write) count pointers, wherein each of the read (write) count pointers is associated with a corresponding queue of the multi-queue device, (2) providing a read (write) count pointer associated with a present queue to read (write) flag logic, (3) adjusting the read (write) count pointer associated with the present queue in response to each read (write) operation performed by the present queue, (4) indicating a read (write) queue switch from the present queue to a next queue, (5) retrieving a read (write) count pointer associated with the next queue; and then (6) simultaneously providing the read (write) count pointer associated with the present queue and the read (write) count pointer associated with the next queue to the read (write) flag logic.

Abstract: A multi-queue memory system is configured to operate in a packet mode. Each packet includes a SOP (start of packet) marker and an EOP (end of packet) marker. A packet status bit (PSB), is used to implement the packet mode. The packet status bit enables partial packet write and partial packet read operations, such that a queue switch can be performed in the middle of packet write or packet read operations. The packet status bit also enables data filtering to be performed between an activated EOP marker and a subsequently received SOP marker (i.e., between the end of one packet and the start of the next packet). Packet mark and re-write and packet mark and re-read operations are also enabled.

Abstract: A multi-port serial buffer having a plurality of queues is configured to include a first set of queues assigned to store write data associated with a first port, and a second set of queues assigned to store write data associated with a second port. The available queues are user-assignable to either the first set or the second set. Write operations to the first set of queues can be performed in parallel with write operations to the second programmable set of queues. In addition, a first predetermined set of queues is assigned to the first port for read operations, and a second predetermined set of queues is assigned to the second port for read operations. Data can be read from the first predetermined set of queues to the first port at the same time that data is read from the second predetermined set of queues to the second port.

Abstract: In a multi-queue memory system, a plurality of read count pointers (one for each queue) are stored in a read address file, and used to generate empty flags. A read count pointer associated with a first queue is retrieved from the read address file, and it is determined whether the first queue should be available for a re-read operation. If so, the retrieved read count pointer is stored as a first read mark value. The read count pointer is incremented in response to each read operation performed from the first queue, thereby creating an adjusted read count pointer. If a re-read operation is to be performed from the first queue, the first read mark value is stored in the read address file. Otherwise, the adjusted first read count pointer is stored in the read address file. Similar operations are performed on the write side of the multi-queue memory system.

Abstract: A serial buffer having a plurality of virtual queues, which can be allocated to include various combinations of on-chip dual-port memory blocks, on-chip internal memory blocks and/or off-chip external memory blocks. The virtual queues are allocated and accessed in response to configuration bits and size bits stored on the serial buffer. Relatively large external memory blocks can be allocated to virtual queues used for data intensive operations, while relatively small and fast dual-port memory blocks can advantageously be allocated to virtual queues used for passing command and status information. The serial buffer provides an efficient and flexible manner for utilizing available memory, which not only minimizes the access latency but also provides a large amount of buffer space to meet different application needs.

Abstract: A multi-port serial buffer having a plurality of queues is configured to include a first set of queues assigned to store write data associated with a first port, and a second set of queues assigned to store write data associated with a second port. The available queues are user-assignable to either the first set or the second set. Write operations to the first set of queues can be performed in parallel with write operations to the second programmable set of queues. In addition, a first predetermined set of queues is assigned to the first port for read operations, and a second predetermined set of queues is assigned to the second port for read operations. Data can be read from the first predetermined set of queues to the first port at the same time that data is read from the second predetermined set of queues to the second port.

Abstract: Multi-Q FIFO memory devices are configured to support a backed-off standard (BOS) mode of operation. This mode of operation enables automatic re-reading of at least one data word previously read from a first queue in the FIFO memory chip during a first FIFO read operation, in response to a queue-switch back to the first queue during a second FIFO read operation. To support this mode of operation, a read counter associated with the first queue is backed-off at least one entry position in response to the queue-switch.

Abstract: In accordance with the invention, a driver circuit is described that permits a single thin gate oxide process to be utilized where a dual oxide process may normally be necessary. Circuits employing only thin gate oxide devices are used as the design basis for a single product with a single set of tooling and manufacturing process to operate within the same timing specifications for a core voltage output drive as well as for a higher system drive.

Abstract: A flag logic circuit is provided for use in a multi-queue memory device having a plurality of queues. A first stage memory stores a flag value for each of the queues in the multi-queue memory device. Flag values are routed from the first stage memory to a flag status bus having a width N in the manner described below. A status bus control circuit receives a signal that identifies the number of queues M actually used by the multi-queue memory device, and in response, generates a repeating pattern of X control values, wherein X is equal to (M?(M mod N))/N+1. A selector circuit sequentially routes X sets of N flag values from the first stage memory to the flag status bus in response to the repeating pattern of X control values. The X sets of N flag values include the flag values associated with the queues actually used.

Abstract: A flag logic circuit includes a first comparator configured to generate a first flag value associated with an active read queue of a multi-queue memory device, and a second comparator configured to generate a second flag value associated with an active write queue of the multi-queue memory device. A dual-port memory is adapted to store a flag value for each queue of the multi-queue memory device. The dual-port memory has a first write port configured to receive the first flag value and a second write port configured to receive the second flag value. A first stage storage element is configured to latch each of the flag values stored in the dual-port memory in response to a first clock signal, such that the flag values are synchronized on an active status bus and flag status bus.

Abstract: FIFO memory devices include a multi-port cache memory device configured to generate a data word along with a plurality of diagnostic bits. These diagnostics bits encode an error correction status of the data word and a path traversal status of the data word through the FIFO memory device. In particular, the diagnostic bits identify all cases of whether the data word includes a corrected or uncorrected error, is without error or is unchecked for errors because the data word did not pass through error detection and correction circuitry within the FIFO memory device.

Abstract: FIFO memory devices are configured to support a pair of hybrid operating modes that enable the FIFO memory device to be depth-expandable with other FIFO memory devices in a collective standard mode of operation. The pair of hybrid operating modes including a first hybrid mode that supports a write interface configured in standard mode and a read interface configured in first-word fall-through (FWFT) mode and a second hybrid mode that supports a write interface configured in FWFT mode and a read interface configured in standard mode.

Abstract: A write counter provides a write count value synchronized with a write clock signal. A read counter provides a read count value synchronized with a read clock signal. The read and write count values are routed through logic, which introduces noise to these values. A first delay circuit generates a first blanking signal, which has a duration corresponding with the duration of the noise introduced to the write count value, in response to the write clock signal. A second delay circuit generates a second blanking signal, which has a duration corresponding with the duration of the noise introduced to the read count value, in response to the second clock signal. The read and write count values are latched into read and write blanking registers, respectively, in response to the first and second blanking signals, respectively, effectively filtering the introduced noise prior to a subsequently performed comparison operation.

Abstract: A multi-queue memory system includes first and second memory blocks. The first memory block includes a first array of memory cells, a first sense amplifier circuit and a second sense amplifier circuit. The second memory block includes a second array of memory cells, a third sense amplifier circuit and a fourth sense amplifier circuit. Each of the sense amplifier circuits is independently controlled. Each queue of the multi-queue system has entries in both the first and second memory blocks. A first queue is accessed by alternately accessing the first and second arrays via the first and third sense amplifier circuits. A second queue is subsequently accessed by alternately accessing the first and second arrays via the second and fourth sense amplifier circuits.

Abstract: A clock signal arbitration method includes arbitrating between first and second request signals generated in respective first and second clock domains that are asynchronously timed relative to each other, to obtain first arbitration results. These first arbitration results identify a relative queue priority between the first and second request signals. Additional steps are performed to transfer the first arbitration results into a third clock domain that is asynchronously timed relative to the first and second clock domains. The transfer operation may include arbitrating the first arbitration results in a third clock domain to obtain second arbitration results that confirm or correct the first arbitration results.

Abstract: An integrated circuit chip includes a plurality of independent FIFO memory devices that are each configured to support all four combinations of DDR and SDR write modes and DDR and SDR read modes and collectively configured to support all four multiplexer, demultiplexer, broadcast and multi-Q operating modes.

Abstract: Multi-Q FIFO memory systems include a plurality of multi-Q first-in first-out (FIFO) memory chips electrically coupled to a data output bus. The plurality of multi-Q FIFO memory chips, which are responsive to respective identification codes ID and respective read chip select signals (/RCS), are configured to support an enhanced multi-chip expansion mode of operation. This expansion mode of operation uses the read chip select signals to control one-at-a-time access of at least two selected multi-Q FIFO memory chips receiving equivalent ID codes and equivalent read addresses to the output data bus during read operations.

Abstract: An integrated circuit memory device includes a quad-port cache memory device and a higher capacity supplemental memory device. These memory devices operate collectively as a high speed FIFO having fast fall through capability and extended data capacity. The FIFO does not require complex arbitration circuitry to oversee reading and writing operations. The supplemental memory device may be an embedded on-chip memory device or a separate off-chip memory device (e.g., DRAM, SRAM). The quad-port cache memory device utilizes a data rotation technique to support bus matching. Error detection and correction (EDC) circuits are also provided to check and correct FIFO read data. The EDC circuits operate without adding latency to FIFO read operations.