Browse Prior Art Database

Method for Improving Half-Cycle Paths to Register Files

IP.com Disclosure Number: IPCOM000108498D
Original Publication Date: 1992-Jun-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 83K

Publishing Venue

IBM

Related People

Arimilli, RK: AUTHOR [+4]

Abstract

Computer systems typically use Register Files in array-intensive applications to minimize chip space and increase functionality. Unlike, edge-triggered latches, certain Register Files have half-cycle paths which make their usage very limiting. Disclosed is a method in which the half-cycle path problem has been eliminated and the Register Files can be used more like conventional edge-triggered latches.

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Method for Improving Half-Cycle Paths to Register Files

       Computer systems typically use Register Files in
array-intensive applications to minimize chip space and increase
functionality.  Unlike, edge-triggered latches, certain Register
Files have half-cycle paths which make their usage very limiting.
Disclosed is a method in which the half-cycle path problem has been
eliminated and the Register Files can be used more like conventional
edge-triggered latches.

      When using edge-triggered latches in a clock synchronous
environment, the time required for data and control to be valid at
the input of all other latches is a full cycle.  However, when
writing to Register Files, the time required for the address, data
and write enables to be valid is a half cycle.  This is because the
Register Files TRANSPARENTLY latch data when the clock is low, while
the latches latch data on the rising EDGE of the clock.  Fig. 1 is an
illustration of the Register File's half cycle-paths.

      With the structure in Fig. 1, the combinatorial logic delays
for the Register File's address, write enables and data cannot exceed
a half cycle.  (The data could take more than a half cycle if all of
the locations are being modified.)  In most aggressive designs,
however, the combinatorial logic delays between latches to latches
and latches to Register Files is typically the same - close to a full
cycle. Thus, this half-cycle limitation does not make Register Files
very attrac...