2REM MOS CIRCUIT SIMULATION BY ITERATIVE TIME ANALYSIS
    3REM---------------------------------------------------------------
  100K=30
  120 MAXNODES=16:MAXDEV=8
  130K=30
  140NTRANS=0:NINPUTS=0:NUNKNOWN=0:MAXCHANGE=0:DT=1
  150 DIM V(MAXNODES),LASTV(MAXNODES),I(MAXNODES),C(MAXNODES)
  160DIM T(MAXDEV),L(MAXDEV),W(MAXDEV),S(MAXDEV),G(MAXDEV),D(MAXDEV)
  170FOR I%=1 TO MAXNODES:C(MAXNODES)=0:NEXT
  180 
  185 PROC_DEFINE_CIRCUIT
  190TMAX=100:DT=1:VCRIT=0.1:OMEGA=1
  200MODE1:PROC_AXES(TMAX)
  201GCOL 0,2
  205LASTT=0
  210FORT%=0TO60
  215FORI%=1TONINPUTS
  216GCOL0,I%
  217IFI%<>VDD PROC_PLOT(LASTT,FN_VOLTAGE(I%,LASTT),T%,FN_VOLTAGE(I%,T%))
  225NEXT
  227LASTT=T%
  230NEXT
  240 
  241GCOL 0,2
  250PROC_INITIALISE_VOLTAGES
  260REPEAT:PROC_TIMESTEP:UNTILT%>=TMAX
  990END
  995REM---------------------------------------------------------------
 1000 DEFPROC_AXES (TMAX)
 1020LOCAL I%
 1025 VDU 5
 1030YFAC=100
 1040MOVE 150,150+5*YFAC:DRAW 150,150:DRAW 1200,150
 1050FOR I%=0 TO 5:MOVE 100,160+I%*YFAC:PRINT ;I% 
 1060MOVE 140,150+I%*YFAC:DRAW 150,150+I%*YFAC:NEXT
 1070XFAC=1050/TMAX
 1110 VDU4
 1120ENDPROC
 1125REM---------------------------------------------------------------
 1130DEFPROC_PLOT (T1,V1,T2,V2)
 1140MOVE 150+XFAC*T1,150+YFAC*V1
 1150DRAW 150+XFAC*T2,150+YFAC*V2
 1160ENDPROC
 1190REM---------------------------------------------------------------
 1590REM---------------------------------------------------------------
 1600DEFPROC_TIMESTEP
 1610LOCAL N%,TEMP
 1612FOR N%=1 TO NINPUTS
 1614LASTV(N%)=V(N%):V(N%)=FN_VOLTAGE(N%,T%):NEXT
 1619V%=MAXNODES+1-NUNKNOWN
 1620FOR N%=V%TOMAXNODES
 1625TEMP=LASTV(N%):Z=V(N%):LASTV(N%)=Z:V(N%)=Z+DT*(Z-TEMP)/(T%-LASTT):NEXT
 1650REPEAT
 1655 MAXCHANGE=0
 1660FOR F%=0 TO MAXNODES:I(F%)=0:NEXT
 1670FORN%=1TONTRANS
 1671S%=S(N%):R%=D(N%):IFV(S%)>V(R%)S%=R%:R%=S(N%)
 1672VDS=V(R%)-V(S%):BETA=K*W(N%)/L(N%):VGE=V(G(N%))-V(S%)-T(N%):IFVGE<0GOTO1680
 1673IFVDS>VGE THENVDS=VGE
 1674IDS=BETA*VDS*(VGE-VDS/2)
 1675I(S%)=I(S%)+IDS
 1676I(R%)=I(R%)-IDS
 1680NEXT
 1690FOR N%=V%TOMAXNODES
 1691VV=V(N%):C1=LASTV(N%)+(DT*I(N%)/(C(N%)))-VV
 1692IFABS(C1)>MAXCHANGE THENMAXCHANGE=ABS(C1)
 1693V(N%)=VV+(OMEGA*C1)
 1709NEXT
 1710UNTIL MAXCHANGE<=VCRIT
 1720FORN%=V%TOMAXNODES:GCOL0,N%-V%+1:PROC_PLOT(LASTT,LASTV(N%),T%,V(N%)):NEXT
 1735LASTT=T%
 1740T%=T%+DT
 1750ENDPROC
 1760REM---------------------------------------------------------------
 2000DEFFN_AN_INPUT
 2010NINPUTS=NINPUTS+1
 2020=NINPUTS
 2030ENDPROC
 2040REM--------------------------------------------------------------
 2050DEFFN_A_NODE
 2060NUNKNOWN=NUNKNOWN+1
 2070=MAXNODES+1-NUNKNOWN
 2080ENDPROC
 2090REM--------------------------------------------------------------
 2100DEFFN_NENH (W%,L%,GATE%,SOURCE%,DRAIN%)
 2110NTRANS=NTRANS+1
 2120C(GATE%)=C(GATE%)+(W%*L%*7*4)
 2130G(NTRANS)=GATE%
 2140S(NTRANS)=SOURCE%
 2150D(NTRANS)=DRAIN%
 2160W(NTRANS)=W%
 2170 L(NTRANS)=L%
 2172T(NTRANS)=1
 2175=NTRANS
 2180ENDPROC
 2190REM--------------------------------------------------------------
 2200DEFFN_PULLUP (W%,L%,SOURCE%,DRAIN%)
 2210NTRANS=NTRANS+1
 2220C(SOURCE%)=C(SOURCE%)+(W%*L%*7*4)
 2230G(NTRANS)=SOURCE%
 2240S(NTRANS)=SOURCE%
 2250D(NTRANS)=DRAIN%
 2260W(NTRANS)=W%
 2270L(NTRANS)=L%
 2275T(NTRANS)=-4
 2280IF W%>L% THEN PRINT "?? Wide pullup transistor no ";ntrans;" ??"
 2290=NTRANS
 2300ENDPROC
 2310REM-------------------------------------------------------------
 2320 DEFPROC_FANOUT (N%,NODE%) 
 2330C(NODE%)=C(NODE%)+(N%*2*2*7*4)
 2340ENDPROC
 2390REM-------------------------------------------------------------
 2400DEFFN_RISING (TSTART,TEND,T)
 2410LOCAL X
 2415X=5*(T-TSTART)/(TEND-TSTART)
 2420IF T<TSTART THEN X=0
 2430IF T>TEND THEN X=5
 2440=X
 2450ENDPROC
 2490REM--------------------------------------------------------------
 2500DEFPROC_INITIALISE_VOLTAGES
 2510LOCAL I%
 2520FOR I%=1 TO NINPUTS
 2530LASTV(I%)=FN_VOLTAGE(I%,0)
 2540V(I%)=LASTV(I%)
 2550NEXT
 2560FOR I%=MAXNODES+1-NUNKNOWN TO MAXNODES
 2570LASTV(I%)=FN_VOLTAGE(I%,0):V(I%)=LASTV(I%)
 2580NEXT
 2590LASTT=0:T%=DT
 2600ENDPROC
 9000REM-------------------------------------------------------------
 9005DEFPROC_DEFINE_CIRCUIT
 9010REM INVERTER TRANSIENT PROBLEM
 9020VDD=FN_AN_INPUT
 9030GND=FN_AN_INPUT
 9040IN=FN_AN_INPUT
 9050OUT=FN_A_NODE
 9060PULLDOWN=FN_NENH (6,2,IN,GND,OUT)
 9070PULLUP=FN_PULLUP (2,6,OUT,VDD)
 9072 OUT2=FN_A_NODE
 9073 PULLDOWN2=FN_NENH (6,2,OUT,GND,OUT2)
 9074 PULLUP2=FN_PULLUP (2,6,OUT2,VDD)
 9075 OUT3=FN_A_NODE
 9076 PD3=FN_NENH(6,2,OUT2,GND,OUT3)
 9077PU3=FN_PULLUP(2,6,OUT3,VDD)
 9084ENDPROC
 9085REM---------------------------------------------------------------
 9090DEFFN_VOLTAGE (NODE%,T%)
 9100LOCAL X
 9102X=1
 9105IF NODE%=IN THEN X=FN_RISING(5,10,T%)
 9106 IF (NODE%=IN) AND (T%>50) THEN =0
 9110IF NODE%=VDD THEN =5
 9120IF NODE%=GND THEN =0
 9135IFT%=0AND(NODE%=OUT ORNODE%=OUT3)THEN=4.8
 9900REM--------------------------------------------------------------
 9991=X