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Circuitry for Precise Starting of Asynchronous Measurement Instrument

IP.com Disclosure Number: IPCOM000105405D
Original Publication Date: 1993-Jul-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Hennet, PP: AUTHOR [+3]

Abstract

Disclosed is circuitry to allow a sequential memory measurement instrument to start precisely from signals received from an asynchronous source.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Circuitry for Precise Starting of Asynchronous Measurement Instrument

      Disclosed is circuitry to allow a sequential memory measurement
instrument to start precisely from signals received from an
asynchronous source.

      A sequential memory system is built to accept data from a
remote hardware system.  The remote hardware system must send n bits
of data to be stored and a 'STROBE' signal that signifies when the n
bits of data are valid.  Since the measurement instrument does not
use the clock from the remote system, the 'STROBE' signal is an
asynchronous event to the measurement instrument.  Circuitry must be
provided to insure that the measurement system does not allow in
partial 'STROBE' signals.  Partial 'STROBE' signals have the
potential to cause unpredictable results at the various latch and
counter portions of the memory system.  Partial 'STROBE' signals
would cause 'slivers' or 'glitches' which can cause latches and
counters to react in unpredictable ways.

      The problem is solved by developing a circuit that will only
allow full width 'STROBE' signals into the memory system.  Figs. 1
and 2 contain the circuitry and timing relationship of the signals
for the solution of this problem.

      The '-Start' signal is a signal that specifies the time at
which data is to start being captured by the measurement instrument.
This is a signal from a program in the measurement instrument or as
the result of the operator pressing a 'START BUTTON'.  The start
signal is a minus active signal, therefore the name '-Start'.  The
circuit is designed to only allow a full width 'STROBE' signal into
the measurement instrument.  The 'STROBE' is defined also as a
negative active signal.  A 'STROBE' is defined as the negative going
edge and the negative level following this edge.  The 'STROBE' signal
is labelled '-Strobe'.  The '-Level' signal is defined as a constant
minus level signal.

      The '-Start' signal is connected to the 'SET'(S) input of the
Flip-Flop(FF).  As long as the start signal is plus, the output of
the Flip-Flop(-Start gated) will always be plus.  When the start
signal goes minus, the next positive going edge of the clock input(C)
will cause the FF to transfer the data input(D) to the output.  Since
the 'D' input is always minus, a minus will be clocked to the output
of the FF.  This circuit then uses the positive going edge of the
'STROBE' signal to provide a gating signal to allow the next full
negative going edge and signal to pass into the system.  As long as
one input to the 'OR' gate is plus, the ou...