| 摘要 |
A multi-port computer register file has shared word lines for read and write ports and storage elements that power down during write operations. Assume that a register file in accordance with the present invention has R read ports and W write ports, and R is greater than W. In such a register file, each register will be accessed by W combined read/write word lines, a single direction line, and R-W read-only word lines. The direction line is asserted during a write operation, and is not asserted during a read operation, and also allows the storage elements comprising each register of the register file to be powered down or enter a high-impedance state during a write operation. During a read operation, the direction line remains deasserted and the storage elements remain powered up and active. For read ports sharing combined read/write word lines with write ports, the direction line is used as a multiplexer signal to enable a read operation at the read port represented by the combined read/write word line. For read ports that are not shared, a read-only word line is used to enable the read operation. During a write operation, the direction line is asserted and the storage elements are powered down or enter a high-impedance state. The direction line is used as a multiplexer signal to enable a write operation at the write port represented by the combined read/write word line. When the write operation ends, the direction line is deasserted, and the storage elements are powered up or leave the high-impedance state, thereby retaining the value written to the storage elements. The present invention provides two important benefits over the prior art. First, by powering down storage elements or placing storage elements in a high-impedance state during write operations, smaller transistors can be used to write values into storage elements. By using smaller transistors, the size and power requirements of the register file are reduced. Second, by using a direction line and combined word lines for read and write ports, the number of horizontal lines running across the register file are reduced.
|
