Browse Prior Art Database

Multiport Static Random Access Memory (RAM) Cell

IP.com Disclosure Number: IPCOM000110196D
Original Publication Date: 1992-Oct-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 1 page(s) / 44K

Publishing Venue

IBM

Related People

Gersbach, JE: AUTHOR

Abstract

The multiport SRAM cell described has fast read capability and two-port independence. The cell is found especially useful for video applications.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 98% of the total text.

Multiport Static Random Access Memory (RAM) Cell

      The multiport SRAM cell described has fast read capability and
two-port independence.  The cell is found especially useful for video
applications.

      Referring to the figure, transistors T1 through T6 represent a
well known 6 device SRAM cell.  Transistors T7, T8, and T9 provide a
fast read port.  The two ports may be operated independently and
asynchronously without interaction except that data at the output of
the read port may change when the same word is written
simultaneously.

      Transistors T7, T8, and T9 may be quite small and still give
good performance if a sense amplifier having a low impedance input is
used to receive data on bit lines R0 and R1.

      The read/write (R/W) port operation is well known and is not
explained here.  The read port operation begins when WORD R is
selected by a positive input.  Either transistor T7 or T8 conduct in
conjunction with transistor T9 depending on the binary state of the
cell (transistors T1 through T4).  Bit lines R0 and R1 are maintained
at a high voltage (close to VH - Vt, where Vt is the threshold
voltage of the N-type transistors) so that node N of selected and
unselected cells need not be fully charged and discharged during a
read operation.

      Transistor T9 could be split into 2 individual transistors so
that the sources of transistors T7 and T8 need not be connected,
thereby offering a possible layout advantage.

      Di...