UCAM-CL-TR-738: High precision timing using self-timed circuits
tech-r...@cl.cam.ac.uk
High precision timing using self-timed circuits
Scott Fairbanks
Technical report UCAM-CL-TR-738, University of Cambridge,
Computer Laboratory, PhD thesis, January 2009, 99 pages.
This document is now available at
http://www.cl.cam.ac.uk/techreports/UCAM-CL-TR-738.html
Abstract:
Constraining the events that demarcate periods on a VLSI chip to precise
instances of time is the task undertaken in this thesis. High speed
sampling and clock distribution are two example applications.
Foundational to my approach is the use of self-timed data control
circuits.
Specially designed self-timed control circuits deliver high frequency
timing signals with precise phase relationships. The frequency and the
phase relationships are controlled by varying the number of self-timed
control stages and the number of tokens they control.
The self-timed control circuits are constructed with simple digital
logic gates. The digital logic gates respond to a range of analog values
with a continuum of precise and controlled delays. The control circuits
implement their functionality efficiently. This allows the gates to
drive long wires and distribute the timing signals over a large area.
Also gate delays are short and few, allowing for high frequencies.
The self-timed control circuits implement the functionality of a FIFO
that is then closed into a ring. Timing tokens ripple through the rings.
The FIFO stages use digital handshaking protocols to pass the timing
tokens between the stages. The FIFO control stage detects the phase
between the handshake signals on its inputs and produces a signal that
is sent back to the producers with a delay that is a function of the
phase relationship of the input signals.
The methods described are not bound to the same process and systematic
skew limitations of existing methods. For a certain power budget, timing
signals are generated and distributed with significantly less power with
the approaches to be presented than with conventional methods.
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University of Cambridge, Computer Laboratory,
Technical Reports (ISSN 1476-2986)
http://www.cl.cam.ac.uk/techreports/