ON 20100202@1:26:27 PM at page: On a web page you were interested in at: http://www.sxlist.com/techref/logic/2to4ndecoder.htm#40211.3686458333 James Newton[JMN-EFP-786] Published and replied to post 40211.3686458333 by ice_chok |Insert 'It's really pretty easy when you think about it: Use 5 2-to-4 decoders, the first one, called "E", is connected to the upper 2 bits of your 4 bit input and it then selects which of the other 4 chips will be enabled. The remaining 4 2-to-4 decoders, called "A", "B","C", and "D", each connect to the lower 2 bits of your 4 bit input and are enabled only when the 4 bit input is on their "bank" of 4 possible outputs. The first of the low bit decoders decodes 0,1,2 and 3, the second decodes 4, 5, 6, and 7, and so on. <TABLE> <TR> <TD colspan=2>input</TD><TD rowspan=1>enable low<BR>bit chip #</TD> </TR> <TR> <TD>decimal</TD><TD>binary</TD> </TR> <TR><TD>0</TD><TD><B>00</B>00</TD><TD>A</TD></TR> <TR><TD>1</TD><TD><B>00</B>01</TD><TD>A</TD></TR> <TR><TD>2</TD><TD><B>00</B>10</TD><TD>A</TD></TR> <TR><TD>3</TD><TD><B>00</B>11</TD><TD>A</TD></TR> <TR><TD>4</TD><TD><B>01</B>00</TD><TD>B</TD></TR> <TR><TD>5</TD><TD><B>01</B>01</TD><TD>B</TD></TR> <TR><TD>6</TD><TD><B>01</B>10</TD><TD>B</TD></TR> <TR><TD>7</TD><TD><B>01</B>11</TD><TD>B</TD></TR> <TR><TD>8</TD><TD><B>10</B>00</TD><TD>C</TD></TR> <TR><TD>9</TD><TD><B>10</B>01</TD><TD>C</TD></TR> <TR><TD>10</TD><TD><B>10</B>10</TD><TD>C</TD></TR> <TR><TD>11</TD><TD><B>10</B>11</TD><TD>C</TD></TR> <TR><TD>12</TD><TD><B>11</B>00</TD><TD>D</TD></TR> <TR><TD>13</TD><TD><B>11</B>01</TD><TD>D</TD></TR> <TR><TD>14</TD><TD><B>11</B>10</TD><TD>D</TD></TR> <TR><TD>15</TD><TD><B>11</B>11</TD><TD>D</TD></TR> </TABLE>' at: '<!-- 40211.3686458333 EOR --><A style="color:#AF4040" TITLE="Click to login and reply" REL="nofollow" HREF="/techref/login/default.asp?req=/techref/update.asp%3Fact=reply%26url=/Techref/logic/new201002.txt%26id=40211.3686458333">+</A>'' but after: '<A TITLE="'.
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Ashley Roll has put together a really nice little unit here. Leave off the MAX232 and keep these handy for the few times you need true RS232! |
 Peter Todd has released source and sample projects for his artwork, including his 3d wireframe cube renderer for the PIC 18f6520 This includes examples of hardware developed with free software tools such as gEDA/gschem/PCB, SDCC, gputils and picp all on Linux. http://petertodd.ca/art/source-code/ |
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