Cadence Tutorial : 8-bit Ripple Carry Adder Schematic & Symbol
Cadence Tutorial : 8-bit Ripple Carry Adder Schematic & Symbol
bug or comment to
Library Create
Invoke icfb program.
- You will see the CIW windows open as shown in .
Create adder8 library.
File->New->Library
In New Library window,
Name : Adder8
Technology File : Don't need a techfile (on the right window)
Inverter Schematic Create
Open schematic window.
File->New->Cellview
In Create New File window,
Library Name : Adder8
Cell Name : inverter
View Name : schematic
Tool : Composer-Schematic
- You will see schematic window open as shown in .
Place nmos transistor.
sch:Add->Component (or "i")
Add Component:click Browse
In Library Browser window,
Library : tsmc25Lib
Cell : nfet3
View : symbol
&When you move mouse into schematic window, nfet3 symbol will
follow your pointer.
Click "mouse L" to place nfet3. ("mouse R" will rotate nfet3 symbol
in clockwise.)
Type "Esc" to exit adding component action.
Place pmos, vdd, and gnd.
- Repeat above procedure for pfet3, vdd, and gnd placement. All components
can be found at the same library (tsmc25Lib or basic). See .
- While Library Browser is open, clicking pmos, vdd, and gnd in cell
field will bring instances. (you don't have to type "Esc" each time.)
Connect each component using wires.
Place mouse pointer on one of the node you want to connect
sch:Add->Wire(narrow) (or "w")
Click "mouse L", drag to other node to connect, and click "mouse
L" to finish.
- Repeat above procedure to finish wiring as shown in .
- To make wire open node at one end (like input and output of inverter),
double-click "mouse L"
Place pins.
sch:Add->Pin (or "p")
In Add Pin window,
Pin Names : A X
Direction : input
&Move mouse to place A pin at input of inverter, then click
"mouse L".
In Add Pin window, change direction to output.
Place X pin at output of inverter.
Add pmos parameters. (W/L)
Click pfet3sch:Edit->Properties->Objects (or "q")
In Edit Object Properties window,&
Width : pPar(&pw&)
Length : pPar(&pl&)
Click OK or Apply
Repeat for nfet3 with width pPar(&nw&) and length pPar(&nl&).
Check and Save
sch:File->Check and Save
Inverter Symbol Create
Open symbol window.
icds:File->New->Cellview
In Create New File window,
Library Name : Adder8
Cell Name : inverter
View Name : symbol
Tool : Composer-Symbol
- You will see symbol window open as shown in .
Draw outline for inverter symbol.
Click line icon on left toolbox of symbol window and draw outline
of inverter.
Finish outline by adding circle.
sym:Add->Shape->Circle
Click "mouse L" on the center of circle, drag and click "mouse
Place pins.
sym:Add->Pin (or "p")
In Add Pin window,
Pin Names : A X
Direction : input
Type : square
&Move mouse to place A pin at input of inverter, then click
"mouse L".
In Add Pin window, change direction to output.
Place X pin at output of inverter.
Add selection box.
sym:Add->Selection Box
In Add Selection Box window, click Automatic.
- Selection box is a boundary to select this symbol in a schematic
which include the current symbol.
Add labels.
sym:Add->Label
In Add Label window,
Label : [@instanceName]
&Place label.
&Repeat Add Label for parameterized attributes.
In Add Label window,
Label : [@pw:pw=%:][@pl:/pl=%:]
See . Comment: The figures have not been updated yet so do not get
confused from the minor differences at the label.
&Place label.
&Repeat Add Label for parameterized attributes.
In Add Label window,
Label : [@nw:nw=%:][@nl:/nl=%:]
Place label.
&See . Comment: The figures have not been updated yet so do not get
confused from the minor differences at the label.
Check and Save
sch:File->Check and Save
Create Other Schematics and Symbols
Draw schematic and symbol for the following components.
- In xor_2 schematic, use wire name to place node name on wire.
- In xor_2 schematic, use inverter we just created.
- If you want resize inverter in xor_2 schematic,
Click inverter and type "q"
In Edit Object Properties window, click Add
&In Add Property window,
Type : float
Value : 10
You will see the sizing of inverter has been changed to 10/2 for pmos.
Create Bit-slice of Adder
Create schematic.
icds:File->New->Cellview
In Create New File window,
Library Name : Adder8
Cell Name : adder_slice
View Name : schematic
Tool : Composer-Schematic
Complete schematic.
Create symbol automatically.
sch:Design->Create Cellview->From Cellview
In Cellview From Cellview window,
Library Name : Adder8
Cell Name : adder_slice
From View Name : schematic
To View Name : symbol
&In Symbol Generation Option window,
Left Pins : CIN
Right Pins : COUT
Top Pins : A B
Bottom Pins : SUM
&- This will display symbol window as shown in .
- Edit symbol as shown in . (Not necessary)
Create 8-bit Adder Schematic
Create schematic.
icds:File->New->Cellview
In Create New File window,
Library Name : Adder8
Cell Name : adder8
View Name : schematic
Tool : Composer-Schematic
Place adder_slice.
Draw wires.
Draw buses.
- Use Add->Wire(wide) (or "W")
Add wire labels on A bus.
sch:Add->Wire Name
In Wire Name window,
Names : A&7:0>
Bus Expansion : on
&Place label on each wire
Repeat for B and S buses.
Add pins and complete schematic.
Check and Save
sch:File->Check and SaveConnect with us
Full-Adder
The half-adder is extremely useful until you want to add more that one
binary digit quantities. The slow way to develop a two binary digit adders would
be to make a truth table and reduce it. Then when you decide to make a three
binary digit adder, do it again. Then when you decide to make a four digit
adder, do it again. Then when ... The circuits would be fast, but development
time would be slow.
Looking at a two binary digit sum shows what we need to extend addition to
multiple binary digits.
11 11 11 --- 110
Look at how many inputs the middle column uses. Our adder needs three
a, b, and the carry from the previous sum, and we can use our two-input
adder to build a three input adder.
Σ is the easy part. Normal arithmetic tells us that if Σ = a +
b + Cin and Σ1 = a + b, then
Σ = Σ1 + Cin.
What do we do with C1 and
C2? Let’s look at three input sums and quickly
calculate:
Cin + a + b = ? 0 + 0 + 0 = 0 0 + 0 + 1 = 1 0 + 1 + 0 = 1 0 + 1 + 1 = 10 1 + 0 + 0 = 1 1 + 0 + 1 = 10 1 + 1 + 0 = 10 1 + 1 + 1 = 11
If you have any concern about the low order bit, please confirm that the
circuit and ladder calculate it correctly.
In order to calculate the high order bit, notice that it is 1 in both
cases when a + b produces a C1. Also, the high order bit
is 1 when a + b produces a Σ1 and
Cin is a 1. So We will have a carry when
C1 OR (Σ1 AND
Cin). Our complete three input adder is:
For some designs, being able to eliminate one or more types of gates can
be important, and you can replace the final OR gate with an XOR gate without
changing the results.
We can now connect two adders to add 2 bit quantities.
A0 is the low order bit of A,
A1 is the high order bit of A, B0
is the low order bit of B, B1 is the high order bit of B,
Σ0is the low order bit of the sum,
Σ1 is the high order bit of the sum, and
Cout is the Carry.
A two binary digit adder would never be made this way. Instead the lowest
order bits would also go through a full adder.
There are several reasons for this, one being that we can then allow a
circuit to determine whether the lowest order carry should be included in the
sum. This allows for the chaining of even larger sums. Consider two different
ways to look at a four bit sum.
111 1&-+ 11&+- 0110 | 01 | 10 1011 | 10 | 11 ----- - | ---- | --- 10001 1 +-100 +-101
If we allow the program to add a two bit number and remember the carry for later, then use that carry in the next sum the program can add any number of bits the user wants even though we have only provided a two-bit adder. Small PLCs can also be chained together for larger numbers. These full adders can also can be expanded to any number of bits space allows. As an example, here’s how to do an 8 bit adder.
This is the same result as using the two 2-bit adders to make a 4-bit adder and then using two 4-bit adders to make an 8-bit adder or re-duplicating ladder logic and updating the numbers.
Each “2+” is a 2-bit adder and made of two full adders. Each “4+” is a 4-bit adder and made of two 2-bit adders. And the result of two 4-bit adders is the same 8-bit adder we used full adders to build. For any large combinational circuit there are generally two approaches to design: you can take simpler circuit or you can design the complex circuit as a complete device. Using simpler circuits to build complex circuits allows a you to spend less time designing but then requires more time for signals to propagate through the transistors. The 8-bit adder design above has to wait for all the Cxout signals to move from A0 + B0 up to the inputs of Σ7. If a designer builds an 8-bit adder as a complete device simplified to a sum of products, then each signal just travels through one NOT gate, one AND gate and one OR gate. A seventeen input device has a truth table with 131,072 entries, and reducing 131,072 entries to a sum of products will take some time. When designing for systems that have a maximum allowed response time to provide the final result, you can begin by using simpler circuits and then attempt to replace portions of the circuit that are too slow. That way you spend most of your time on the portions of a circuit that matter.
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的翻译结果:
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For the optimization of Wallace tree adding, the series formulas of full-adder and 4-2 Compressor realization are introduced to guidance the selection.
对于最优Wallace树型加法实现，提出了全加器和4-2 compressor电路实现 Wallace树加法所需的关键加法路径级数公式以指导实现选择；
A full-adder optimization design method in DSP
DSP芯片中全加器电路的优化设计
Some Methods
Designing Full-adder
全加器的几种设计方法
Realization of a High Performances CMOS Full-Adder
高性能CMOS全加器设计
SUPERPIPELINED S-ARY PRNS DIGITAL FULL-ADDER
超级流水S进制PRNS数母全加器
For the optimization of Wallace tree adding, the series formulas of full-adder and 4-2 Compressor realization are introduced to guidance the selection.
对于最优Wallace树型加法实现，提出了全加器和4-2 compressor电路实现 Wallace树加法所需的关键加法路径级数公式以指导实现选择；
A full-adder optimization design method in DSP
DSP芯片中全加器电路的优化设计
Some Methods
Designing Full-adder
全加器的几种设计方法
Realization of a High Performances CMOS Full-Adder
高性能CMOS全加器设计
SUPERPIPELINED S-ARY PRNS DIGITAL FULL-ADDER
超级流水S进制PRNS数母全加器
Programmable and Integrable Hybrid Optoelectronic Liquid Crystal Encoded 32 bit Full-adder Module
可编程可集成光电混合液晶编码32比特加法器模块
At 1.8 V supply voltage,the operation time of the full-adder is 0.851 ns,and the average power dissipation is 3.35 μW at a frequency of 50 MHz.
在 1 .8V工作电压下 ,获得了运算时间为 0 .85 lns,平均功耗 ( 5 0 MHz) 3.35 μW的良好特性。
By applying switch-signal theory, the interaction between MOS transmission switching transistor and current signal in current-mode circuits is analyzed, and the theory of transmission current-switches which is suitable to current-mode CMOS circuits is proposed. The circuits such as ternary full-adder, etc.
本文应用开关信号理论对电流型CMOS电路中MOS传输开关管与电流信号之间的相互作用进行了分析,并提出了适用于电流型CMOS电路的传输电流开关理论。
In this paper, one-bit ternary full-adder and full-multiplier are designed by using ternary universal-logic-gate-UkS based upon modular algebra.
本文利用基于模代数的三值通用逻辑门——U_k,设计了一位三值全加法器和全乘法器电路。
Two circuit structures which are the optimized multiplier with full-adder array and the serial-parallel multiplier with pipeline inside are put forward.
提出了普通阵列乘法电路的改进结构和含流水线的串并乘法电路(SPM)结构。
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