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Subject: Synchronous Decade Counters
Date: Sat, 1 Jan 2011 15:23:56 +0200
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD><TITLE>Synchronous Decade Counters</TITLE>
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width=3D200 height=3D60>=20
<H1 align=3Dcenter><FONT color=3Dpurple><I>Synchronous<BR>Decade =
Counters</I></FONT>=20
</H1>
<BLOCKQUOTE><B>Similar to an asynchronous decade counter, a <FONT=20
  color=3D#ff0080><BIG><I>synchronous decade counter =
</I></BIG></FONT>counts from=20
  0 to 9 and then recycles to 0 again. &nbsp;This is done by forcing the =
1010=20
  state back to the 0000 state. &nbsp;This so called <FONT=20
  color=3D#0080ff>truncated sequence</FONT> can be constructed by the =
following=20
  circuit.</B> </BLOCKQUOTE>
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pg"=20
width=3D513 height=3D145>=20
<P align=3Dcenter>
<TABLE cellPadding=3D2>
  <TBODY>
  <TR>
    <TD><IMG border=3D0 alt=3DSequence=20
      =
src=3D"http://www.eelab.usyd.edu.au/digital_tutorial/part2/pics/count06t.=
jpg"=20
      width=3D251 height=3D196></TD>
    <TD><B>From the sequence on the left, we notice that:</B>=20
      <UL>
        <LI><B>Q0 toggles on each clock pulse</B>.=20
        <LI><B>Q1 changes on the next clock pulse each time Q0=3D1 and =
Q3=3D0</B>.=20
        <LI><B>Q2 changes on the next clock pulse each time =
Q0=3DQ1=3D1</B>.=20
        <LI><B>Q3 changes on the next clock pulse each time Q0=3D1, =
Q1=3D1 and Q2=3D1=20
        (count 7), or when Q0=3D1 and Q3=3D1 (count 9)</B>.=20
</LI></UL></TD></TR></TBODY></TABLE>
<BLOCKQUOTE><B>These characteristics are implemented with the AND/OR =
logic=20
  connected as shown in the logic diagram =
above.<BR><BR></B></BLOCKQUOTE>
<P><BR><BR><BR>
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