The following deck simulates a four-bit binary adder, using several subcircuits to describe various pieces of the overall circuit.

Example:

ADDER - 4 BIT ALL-NAND-GATE BINARY ADDER
*** SUBCIRCUIT DEFINITIONS
.SUBCKT NAND 1 2 3 4
* NODES: INPUT(2), OUTPUT, VCC
Q1 9 5 1 QMOD
D1CLAMP 0 1 DMOD
Q2 9 5 2 QMOD
D2CLAMP 0 2 DMOD
RB 4 5 4K
R1 4 6 1.6K
Q3 6 9 8 QMOD
R2 8 0 1K
RC 4 7 130
Q4 7 6 10 QMOD
DVBEDROP 10 3 DMOD
Q5 3 8 0 QMOD
.ENDS NAND

Continue 4 Bit adder:

.SUBCKT ONEBIT 1 2 3 4 5 6
* NODES: INPUT(2), CARRY-IN, OUTPUT, CARRY-OUT, VCC
X1 1 2 7 6 NAND
X2 1 7 8 6 NAND
X3 2 7 9 6 NAND
X4 8 9 10 6 NAND
X5 3 10 11 6 NAND
X6 3 11 12 6 NAND
X7 10 11 13 6 NAND
X8 12 13 4 6 NAND
X9 11 7 5 6 NAND
.ENDS ONEBIT

.SUBCKT TWOBIT 1 2 3 4 5 6 7 8 9
* NODES: INPUT - BIT0(2) / BIT1(2), OUTPUT - BIT0 / BIT1,
* CARRY-IN, CARRY-OUT, VCC
X1 1 2 7 5 10 9 ONEBIT
X2 3 4 10 6 8 9 ONEBIT
.ENDS TWOBIT

.SUBCKT FOURBIT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
* NODES: INPUT - BIT0(2) / BIT1(2) / BIT2(2) / BIT3(2),
* OUTPUT - BIT0 / BIT1 / BIT2 / BIT3, CARRY-IN, CARRY-OUT, VCC
X1 1 2 3 4 9 10 13 16 15 TWOBIT
X2 5 6 7 8 11 12 16 14 15 TWOBIT
.ENDS FOURBIT

*** DEFINE NOMINAL CIRCUIT
.MODEL DMOD D
.MODEL QMOD NPN(BF=75 RB=100 CJE=1PF CJC=3PF)
VCC 99 0 DC 5V
VIN1A 1 0 PULSE(0 3 0 10NS 10NS 10NS 50NS)
VIN1B 2 0 PULSE(0 3 0 10NS 10NS 20NS 100NS)
VIN2A 3 0 PULSE(0 3 0 10NS 10NS 40NS 200NS)
VIN2B 4 0 PULSE(0 3 0 10NS 10NS 80NS 400NS)
VIN3A 5 0 PULSE(0 3 0 10NS 10NS 160NS 800NS)
VIN3B 6 0 PULSE(0 3 0 10NS 10NS 320NS 1600NS)
VIN4A 7 0 PULSE(0 3 0 10NS 10NS 640NS 3200NS)
VIN4B 8 0 PULSE(0 3 0 10NS 10NS 1280NS 6400NS)
X1 1 2 3 4 5 6 7 8 9 10 11 12 0 13 99 FOURBIT
RBIT0 9 0 1K
RBIT1 10 0 1K
RBIT2 11 0 1K
RBIT3 12 0 1K
RCOUT 13 0 1K

*** (FOR THOSE WITH MONEY (AND MEMORY) TO BURN)
.TRAN 1NS 6400NS
.END