The present invention includes a memory subsystem comprising at least two semiconductor devices (15, 16 , 17), including at least one memory device (15, 16 or 17), connected to a bus (18), where the bus includes a plurality of bus lines for carrying substantially all address, data and control information needed by said memory devices (15, 16 or 17), where the control information includes device-select information and the bus (18) has substantially fewer bus lines than the number of bits in a single address, and the bus (18) carries device-select information without the need for separated device-select lines connected directly to individual devices. The present invention also includes a protocol for master and slave devices to communicate on the bus (18) and for registers in each device to differentiate each device and allow bus requests to be directed to a single or to all devices (15, 16, 17). The present invention includes modifications to prior-art devices to allow them to implement the new features of this invention. In a preferred implementation, 8 bus data lines and an Address Valid bus line carry address, data and control information for memory addresses up to 40 bits wide.

Integrated circuit I/O using a high performance bus interface

A semiconductor memory device comprises memory cells, a bitline connected to the memory cells, a read circuit including a precharge circuit, and a first transistor connected between the bitline and the read circuit, wherein a first voltage is applied to a gate of the first transistor when the precharge circuit precharges the bitline, and a second voltage which is different from the first voltage is applied to the gate of the first transistor when the read circuit senses a change in a voltage of the bitline.

Semiconductor memory device.

A memory system includes a memory, an input circuit and a logic circuit. The input circuit is coupled to receive a memory address and, during a write operation, the corresponding write data to be written into the SRAM. The logic circuit causes the write data to be stored in the input circuit for the duration of any sequential read operations immediately following the write operation and then to be read into the memory during subsequent write operation. During the read operation, data which is stored in the write data storage registers prior to being read into the memory can be read out from the memory system should the address of one or more read operations equal the address of the data to be written into the memory while temporarily stored in the write data storage registers. Thus, no "bus turnaround" down time is experienced by the system thereby increasing the bandwidth of the system. The system can operate in a single pipeline mode or a dual pipeline mode.

Fully synchronous pipelined RAM

In accordance with the present invention, a cache memory subsystem includes a processor, a cache control unit and a SRAM serving as the cache memory. The SRAM is a synchronous SRAM. The cache control unit provides appropriately timed control signals to the SRAM when the processor is accessing the cache memory. The SRAM can be either a pipelined architecture SRAM (register output SRAM) or a flow-through access architecture SRAM (latch output SRAM). The cache control unit is selectably configured to operate in a pipelined mode (1-1-1) or a flow-through (2-2) mode. The cache control unit is configured in the 1-1-1 mode when the SRAM is a pipelined architecture SRAM having a clock rate equal to the processor. When the SRAM is a flow-through architecture SRAM that cannot be clocked at the same rate as the processor, the cache control unit is configured in the 2-2 mode and the SRAM is clocked at a clock rate half of the processor clock rate.

Multiple-mode external cache subsystem

A method and structure facilitates the debugging and test coverage capabilities of a microprocessor. A microprocessor having memory arrays, a debug block, and one or more built-in-self-test (BIST) engines is disclosed. The debug block is capable of driving control information out onto a state machine output bus in response to an event and the control information can be selectively used to control signature analysis or recording elements of the microprcessor, such as multiple-input-shift-registers and first-in-first-out devices, that facilitate in the monitoring and debugging of the microprocessor. The signature and recording elements may or may not be contained within the one or more BIST engines and may or may not be used in conjunction with the memory arrays or BIST engine(s) of the microprocessor.

Method and system for flexible control of BIST registers based upon on-chip events

A single chip cache address comparator with an on-chip static RAM for storing and checking the cache tags of an external cache memory. This cache address comparator has a built-in incrementing counter which controls the burst fill of the internal cache of a 68020/68030 microprocessor from the associated external cache memory within the required five processor clock cycles. Further, additional on-chip control logic is provided to control the 68020/68030 system buses to coordinate a burst fill operation.

Jr. Arthur F. Cochcroft

Papers

Cache address comparator with sram having burst addressing control