Custom Single-purpose Processors

Custom Single-purpose processors

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A single-purpose processor is a digital system intended to solve a specifc computation task. A custom single purpose processor purpose  processor to execute a specifc task within the ES An embedded system designer choosing to use a custom single-purpose, rather than a generalpurpose, processor to implement part o a system!s unctionality may achieve several benefts.  –

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perormance may be ast si"e may be small

#ere its start with a review o combinational and se$uential design, and then describe a method or converting programs to custom single-purpose processors.

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A single-purpose processor is a digital system intended to solve a specifc computation task. A custom single purpose processor purpose  processor to execute a specifc task within the ES An embedded system designer choosing to use a custom single-purpose, rather than a generalpurpose, processor to implement part o a system!s unctionality may achieve several benefts.  –

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perormance may be ast si"e may be small

#ere its start with a review o combinational and se$uential design, and then describe a method or converting programs to custom single-purpose processors.

Combinational logic design •

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A combinational circuit is circuit is a digital circuit whose current ent inputs inputs%% output is purely a function of its curr such a circuit has no memory o past inputs. inputs . A transistor is the basic electrical component o digital systems. Combinations o transistors orm components called logic gates gates.. The basic principle of a NPN transistor to act as a switch is, is, a high voltage &typically '( )olts as logic *+ is applied to the gate, the transistor conducts,, so current ows. hen low voltage conducts &reer to as logic , typically ground,+ is applied to the gate, the transistor does not conduct. conduct.

Creation o /ates using transistors

0asic logic gates

Combinational circuit design •

12 y is * i a is e$ual to *, or b and

c is e$ual to *. " is * i a is e$ual to * and b is e$ual to * or i b or c is e$ual to *, but not both.

34 5level combinational components •

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34 level uses combination components that are more power ull than gates. Such Components are  –

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6ultiplexer 7ecoder Adder Comparator A89

6ultiplexer

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A multiplexor, sometimes called a selector, allows only one of its data inputs to pass through to the output according to the selection pins inputs. : there are m data inputs, then there are log2(m) select lines .

7ecoder •

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A decoder converts its binary input  into a one!hot output ". #"ne!hot# means that exactly one o the output lines can be * at a given time.  4hus, i there are n outputs, then there must be log2(n) inputs.

Adder •

An adder adds two n!bit binary inputs  $ and %, generating an n!bit output sum along with an output carry.

Comparator •

A comparator compares two n!bit binary inputs $ and %, generating outputs that indicate whether $ is less than, e&ual to, or greater than %.

A89 •

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An $' (arithmetic!logic unit) can  perform a variety of arithmetic and logic unctions on its n-bit inputs  $ and %. The select lines  choose the current function* if there are m possible functions, then there must be at least log2(m) select lines.

Se$uential logic design

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A se&uential circuit is a digital circuit whose outputs are a function of the current as well as previous input values. :n other words, se$uential logic possesses memory. ;ne o the most basic se$uential circuits is the +ip!+op. $ +ip!+op stores a single bit.

3egisters

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A register stores n bits from its n!bit data input , with those stored bits appearing at its output ".  $ register usually has at least two control inputs, cloc and load. -or a rising-edge-triggered register, the inputs  are only stored when load is  and cloc is rising rom  to *.

Shitregiste rs

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A shit register has a one-bit data input , and at least two control inputs cloc and shift. /hen cloc isrising and shift is , the value of  is stored in the (n)0th bit, while the (n)0th bit is stored in the &n*+!th bit, and likewise, until the second bit is stored in the frst bit.  4he frst bit is typically shited out, meaning it appears over an output 1.

 4ypes o S3!s

ou want to construct a clock divider Slow down your pre-existing clock so that you output a * or every our clock cycles.

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