2023-04-22 11:29:44 +02:00
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<!DOCTYPE html>
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<title>XSCHEM TUTORIAL: SYMBOL GENERATORS</title>
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<div class="content">
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<!-- navigation buttons -->
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<a href="xschem_man.html" class="home">UP</a>
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<!-- slide title -->
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<h1> TUTORIAL: SYMBOL GENERATORS</h1>
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2023-04-23 11:06:08 +02:00
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<p>
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It is possible to insert a symbol by referencing a generator script instead of a <kbd>.sym</kbd> file.
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When inserting the symbol select the <kbd>All</kbd> checkbox to see all files , select the generator script,
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then in the File/Search textbox add two parenthesis <kbd>()</kbd> (or put required parameters in
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between, like <kbd>(buf)</kbd>)
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</p>
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<img src="symbol_generators01.png">
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<p>
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The symbolgen generator in this example takes either a <kbd>(buf)</kbd> or a <kbd>(inv)</kbd> parameter
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to generate a buffer or an inverter, respectively. If no parameters are given (empty parentheses) a buffer
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is generated.<br>
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In this example a tcl script is used, you can use any language you like.
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</p>
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<pre class="code">
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#!/bin/sh
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# the next line restarts using wish \
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exec tclsh "$0" "$@"
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set arg1 [lindex $argv 0]
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if { $arg1 eq {inv}} {
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puts {v {xschem version=3.1.0 file_version=1.2}
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K {type=subcircuit
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verilog_primitive=true
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vhdl_primitive=true
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vhdl_format="@@Y <= not @@A after 90 ps;"
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verilog_format="assign #90 @@Y = ~@@A ;"
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format="@name @pinlist @symname ROUT=@ROUT"
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template="name=x1 ROUT=1000"
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schematic=inv_ngspice.sch}
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L 4 -40 0 -20 0 {}
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L 4 -20 -20 20 0 {}
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L 4 -20 -20 -20 20 {}
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L 4 -20 20 20 0 {}
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L 4 30 -0 40 -0 {}
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B 5 37.5 -2.5 42.5 2.5 {name=Y dir=out }
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B 5 -42.5 -2.5 -37.5 2.5 {name=A dir=in }
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A 4 25 -0 5 180 360 {}
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T {@symname} -47.5 24 0 0 0.3 0.3 {}
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T {@name} 25 -22 0 0 0.2 0.2 {}
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T {Y} 7.5 -6.5 0 1 0.2 0.2 {}
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T {A} -17.5 -6.5 0 0 0.2 0.2 {}
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T {ROUT=@ROUT} -25 -42 0 0 0.2 0.2 {}
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}
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} else {
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puts {v {xschem version=3.1.0 file_version=1.2}
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K {type=subcircuit
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verilog_primitive=true
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vhdl_primitive=true
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vhdl_format="@@Y <= @@A after 90 ps;"
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verilog_format="assign #90 @@Y = @@A ;"
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format="@name @pinlist @symname ROUT=@ROUT"
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template="name=x1 ROUT=1000"
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schematic=buf_ngspice.sch}
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L 4 20 0 40 0 {}
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L 4 -40 0 -20 0 {}
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L 4 -20 -20 20 0 {}
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L 4 -20 -20 -20 20 {}
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L 4 -20 20 20 0 {}
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B 5 37.5 -2.5 42.5 2.5 {name=Y dir=out }
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B 5 -42.5 -2.5 -37.5 2.5 {name=A dir=in }
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T {@symname} -47.5 34 0 0 0.3 0.3 {}
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T {@name} 25 -22 0 0 0.2 0.2 {}
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T {Y} 7.5 -6.5 0 1 0.2 0.2 {}
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T {A} -17.5 -6.5 0 0 0.2 0.2 {}
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T {ROUT=@ROUT} -25 -42 0 0 0.2 0.2 {}
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}
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}
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</pre>
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<p>
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The <kbd>generators/test_symbolgen.sch</kbd> is a test schematic that places two instancs of this
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symbol generator, one as <kbd>symbolgen(buf)</kbd> and one as <kbd>symbolgen(inv)</kbd>.
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The schematic implementations of these symbols are defined by the generator using a <kbd>schematic</kbd>
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attribute. The buffer will use <kbd>buf_ngspice.sch</kbd> and the inverter will
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use <kbd>inv_ngspice.sch</kbd>, these reused example schematics are present in
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the <kbd>ngspice/</kbd> directory.
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</p>
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<img src="symbol_generators02.png">
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<p>
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The following is the extracted netlist from this example:
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</p>
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<pre class="code">
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** sch_path: /home/schippes/xschem-repo/trunk/xschem_library/generators/test_symbolgen.sch
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**.subckt test_symbolgen
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x1 IN_INV IN symbolgen_inv ROUT=1200
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x3 IN_BUF IN symbolgen_buf ROUT=1200
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C1 IN_BUF 0 100f m=1
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C2 IN_INV 0 100f m=1
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**** begin user architecture code
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.param vcc=1.8
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Vin in 0 pwl 0 0 10n 0 10.1n 1.8 20n 1.8 20.1n 0
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.control
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save all
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tran 0.2n 30n uic
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write test_symbolgen.raw
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.endc
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**** end user architecture code
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**.ends
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* expanding symbol: symbolgen(inv) # of pins=2
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** sym_path: /home/schippes/xschem-repo/trunk/xschem_library/generators/symbolgen
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** sch_path: /home/schippes/xschem-repo/trunk/xschem_library/ngspice/inv_ngspice.sch
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.subckt symbolgen_inv Y A ROUT=1000
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*.ipin A
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*.opin Y
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B1 net1 0 V = 'VCC/2*(1-tanh((V(A1)-VCC/2)*100))'
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R1 Y1 net1 'ROUT' m=1
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C1 A1 0 8f m=1
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C2 Y1 0 8f m=1
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V1 Y Y1 0
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.save i(v1)
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V2 A1 A 0
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.save i(v2)
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.ends
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* expanding symbol: symbolgen(buf) # of pins=2
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** sym_path: /home/schippes/xschem-repo/trunk/xschem_library/generators/symbolgen
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** sch_path: /home/schippes/xschem-repo/trunk/xschem_library/ngspice/buf_ngspice.sch
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.subckt symbolgen_buf Y A ROUT=1000
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*.ipin A
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*.opin Y
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B1 net1 0 V = 'VCC/2*(1+tanh((V(A1)-VCC/2)*100))'
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R1 Y1 net1 'ROUT' m=1
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C3 Y1 0 8f m=1
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C1 A1 0 4f m=1
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V1 Y Y1 0
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.save i(v1)
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V2 A1 A 0
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.save i(v2)
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.ends
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.end
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</pre>
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<p>
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This approach allows to create polymorphic symbols. Multiple parameters may be given to the generator script,
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like <kbd>symbolgen(inv,hv,100)</kbd>. Xschem will call the symbolgen script with the following command:
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<kbd>symbolgen inv hv 100</kbd> and take the standard output from the script as the symbol
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file to load and display.
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</p>
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<br><br><br>
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2023-04-22 11:29:44 +02:00
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