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<H1><A NAME="SECTION000240000000000000000">
DpgenAdsb2f</A>
</H1>
<UL>
<LI><SPAN CLASS="textbf">Name</SPAN> : DpgenAdsb2f - Adder/Substractor Macro-Generator
</LI>
<LI><SPAN CLASS="textbf">Synopsys</SPAN> :
<PRE>
Generate ( 'DpgenAdsb2f', modelname
, param = { 'nbit' : n
, 'physical' : True
, 'behavioral' : True
}
)
</PRE>
</LI>
<LI><SPAN CLASS="textbf">Description</SPAN> : Generates a <code>n</code> bits adder/substractor named <code>modelname</code>.
</LI>
<LI><SPAN CLASS="textbf">Terminal Names</SPAN> :
<UL>
<LI><SPAN CLASS="textbf">i0</SPAN> : First operand (input, <code>n</code> bits)
</LI>
<LI><SPAN CLASS="textbf">i1</SPAN> : Second operand (input, <code>n</code> bits)
</LI>
<LI><SPAN CLASS="textbf">q</SPAN> : Output operand (ouput, <code>n</code> bits)
</LI>
<LI><SPAN CLASS="textbf">add_sub</SPAN> : Select addition or substraction (input, 1 bit)
</LI>
<LI><SPAN CLASS="textbf">c31</SPAN> : Sarry out. In unsigned mode, this is the overflow (output, 1 bit)
</LI>
<LI><SPAN CLASS="textbf">c30</SPAN> : Used to compute overflow in signed mode : <code>overflow = c31 xor c30</code> (output, 1 bit)
</LI>
<LI><SPAN CLASS="textbf">vdd</SPAN> : power
</LI>
<LI><SPAN CLASS="textbf">vss</SPAN> : ground
</LI>
</UL>
</LI>
<LI><SPAN CLASS="textbf">Parameters</SPAN> : Parameters are given in the map <code>param</code>.
<UL>
<LI><SPAN CLASS="textbf">nbit</SPAN> (mandatory) : Defines the size of the generator
</LI>
<LI><SPAN CLASS="textbf">physical</SPAN> (optional, default value : False) : In order to generate a layout
</LI>
<LI><SPAN CLASS="textbf">behavioral</SPAN> (optional, default value : False) : In order to generate a behavior
</LI>
</UL>
</LI>
<LI><SPAN CLASS="textbf">How it works</SPAN> :
<UL>
<LI>If the <code>add_sub</code> signal is set to <code>zero</code>, an addition is performed, otherwise it's a substraction.
</LI>
<LI>Operation can be either signed or unsigned. In unsigned mode <code>c31</code> is the overflow ; in signed mode you have to compute overflow by <SPAN CLASS="textit">XORing</SPAN> <code>c31</code> and <code>c30</code>
</LI>
</UL>
</LI>
<LI><SPAN CLASS="textbf">Example</SPAN> :
<PRE>
from stratus import *
class inst_ADSB2F ( Model ) :
def Interface ( self ) :
self.in1 = SignalIn ( "in1", 8 )
self.in2 = SignalIn ( "in2", 8 )
self.out = SignalOut ( "o", 8 )
self.as = SignalIn ( "as", 1 )
self.c0 = SignalOut ( "c0", 1 )
self.c1 = SignalOut ( "c1", 1 )
self.vdd = VddIn ( "vdd" )
self.vss = VssIn ( "vss" )
def Netlist ( self ) :
Generate ( 'DpgenAdsb2f', 'adder_8'
, param = { 'nbit' : 8
, 'physical' : True
}
)
self.I = Inst ( 'adder_8', 'inst'
, map = { 'i0' : self.in1
, 'i1' : self.in2
, 'add_sub' : self.as
, 'q' : self.out
, 'c30' : self.c0
, 'c31' : self.c1
, 'vdd' : self.vdd
, 'vss' : self.vss
}
)
def Layout ( self ) :
Place ( self.I, NOSYM, Ref(0, 0) )
</PRE>
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