US 6,556,501 B1 · Multi-port computer register file having shared word lines for read and write ports and storage elements that power down or enter a high-impendance state during write operations

Abstract

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.

Claims21

Dependent claims

A portion of a register file comprising:

a storage element for storing a value;
a read line for receiving a value from the storage element;
a write line for providing to the storage element a value to be written to the storage element;
a combined read/write word line that assumes an active state during read and write operations;
a direction line that assumes a write direction state during a write operation and a read direction state during a read operation;
and
a multiplexer uniquely associated with the storage element that couples the read line to the storage element to read a value from the storage element when the combined read/write word line is active and the direction line assumes the read direction state, and couples the write line to the storage element to write a value to the storage element when the combined read/write word line assumes the active state and the direction line assumes the write direction state.

4 more elements

A register file comprising:

an array of storage elements configured into rows of words and columns of bit positions, wherein each storage element associated with a word and a bit position;
at least one combined read/write word line associated with each row of words, wherein each combined read/write word line assumes an active state during a read or write operation to the row of words with which it is associated;
a direction line associated with each row of words, wherein each direction line assumes a write direction state during a write operation to the row of words with which it is associated and assumes a read direction state during a read operation to the row of words with which it is associated;
at least one read line associated with each column of bit positions, for selectively receiving a value from one of the storage elements in the column of bit positions;
at least one write line associated with each column of bit positions, for selectively providing a value to one of the storage elements in the column of bit positions;
and
a plurality of multiplexers that uniquely correspond to the plurality of storage elements, wherein each multiplexer couples a read line to a storage element to read a value from the storage element when the combined read/write word line associated with the storage element is active and the direction line associated with the storage element assumes the read direction state, and couples the write line to the storage element to write a value to the storage element when the combined read/write word line assumes the active state and the direction line assumes the write direction state.

4 more elements

Dependencies are inferred from the claim text.

Multi-port computer register file having shared word lines for read and write ports and storage elements that power down or enter a high-impendance state during write operations

Life of this patent

Multi-port computer register file having shared word lines for read and write ports and storage elements that power down or enter a high-impendance state during write operations

Life of this patent

Abstract

Claims21