5 A=0
   10  DIM C% 400
   20  *KEY10"OLD|M "
   30  *FX12,25
   40  
   50  VDU23,240,&FF,0,0,0,0,0,0,0
   60  VDU23,241,&FF,0,&FF,&FF,&FF,&FF,0,0
   70  VDU23,242,0,0,0,0,0,0,0,&FF
   80  VDU23,243,0,0,&FF,&FF,&FF,&FF,0,&FF
  100  MODE 7 
  110  *FX4,0
  120  VDU23,1,1;0;0;0;0 
  130  
  140  PRINT"�DIGITAL ANALYSER"
  150  PRINT''"ƒ1....USER PORT"
  160  PRINT"ƒ2....SIMULATION"
  170  REPEAT
  180  A$=GET$
  190  UNTIL INSTR("12",A$)
  200  IF A$="2" THEN GOTO 370
  210  
  220  
  230  REM"�USER PORT
  240  MODE0:PROCinit
  250  A%=0:B%=0:PROCgetdata
  260  A=0
  270  CALL &900
  280  F=INT(1/((A%+B%)*9.0E-6)) 
  282  PRINTTAB(1,29)"BIT 7| FREQUENCY=";F;" HZ      "
  290  PRINTTAB(33,29)"LOW COUNT=";B%;"    "
  300  PRINTTAB(53,29)"HIGH COUNT=";A%;"    "
  320  REPEAT
  330  PROCkeys
  340  UNTIL FALSE
  350  
  360  
  370  REM"�DATA SIMULATOR
  390  MODE 0:PROCinit
  392  PROCdata
  400  PRINTTAB(30,29)"SIMULATION"
  410  
  450  REPEAT
  460  PROCkeys
  470  UNTIL FALSE 
  480  
  490  DEFPROCkeys
  500  REPEAT
  510  IF A=136 THEN ?&7C=?&7C-1
  520  IF A=137 THEN ?&7C=?&7C+1
  532  IF INSTR("Pp",CHR$(A))THENCALLD%
  540  IF ?&7C<1 THEN ?&7C=1
  550  IF ?&7C>70 THEN ?&7C=70
  560  CALLC%
  570  PROCbits
  580  A=GET
  590  UNTIL A=13
  600  ENDPROC
  610  
  620  
  630  DEFPROCbits
  640  W=?((!&80+71)-?&7C)
  650  PRINTTAB(1,3);
  660  FOR P=7 TO 0 STEP -1 
  670  IF W AND 2^P THEN PRINT"1"; ELSE PRINT"0";
  680  NEXT 
  690  PRINTTAB(15,VPOS)"&";STR$~(W)"  "; 
  700  PRINTTAB(25,VPOS)STR$(W)"  ";
  710  IF W>31 AND W<127 THEN C$=CHR$(W) ELSE C$=" "
  720  PRINTTAB(35,VPOS)C$;
  730  ENDPROC
  740  
  750  DEFPROCdata
  760  REM"…read USER PORT
  770  B%=?&FE60
  780  REM"…BIT MASK 
  790  B%=B% AND &0F
  800  FOR Q=!&80 TO !&80+70
  810  ?&78=(Q-!&80) MOD 32
  820  PROClogic
  830  ?Q=?&78
  840  NEXT
  850  ENDPROC
  860  
  870  DEFPROClogic
  880  E%=?&78 MOD 2
  890  ?&78=?&78 DIV 2
  900  A%=?&78 AND &0F
  910  IF A%>B% THEN ?&78=?&78 OR &10
  920  IF A%=B% THEN ?&78=?&78 OR &20 
  930  IF A%<B% THEN ?&78=?&78 OR &40
  940  IF E% THEN ?&78=?&78 OR &80
  950  ENDPROC
  960  
  970  DEFPROCinit
  980  IF ?C%<>&A9 THEN OSCLI("LOAD"+CHR$(34)+"Dump"+CHR$(34)+" "+STR$~(C%))
  990  *FX4,1
 1000  VDU23,1,0;0;0;0;0
 1010  REM"…C%= plot routine
 1020  D%=C%+&6E:REM"…print routine
 1030  !&80=&D10
 1040  ?&7C=70:REM"…cursor position 
 1050  PRINTTAB(30,1)"DIGITAL ANALYSER"
 1060  FOR S=6 TO 27 STEP 3
 1070  PRINT TAB(1,S)"BIT ";(S-6)/3;"|";
 1080  NEXT
 1090  PRINTTAB(1,2)"76543210" 
 1100  ENDPROC
 1110  
 1120  DEFPROCgetdata
 1130  FOR I%=0 TO 2 STEP 2
 1140  P%=&900
 1150  [OPTI%
 1160  \"…disable interupts and
 1170  \"…set the data counter
 1180  SEI:LDY #70
 1190  .synclow
 1200  BIT &FE60:BPL synclow
 1210  .synchigh
 1220  BIT &FE60:BMI synchigh
 1230  .get
 1270  \"…read the USER PORT and
 1280  \"…store as it goes negative
 1282  .loop1
 1290  LDA &FE60:BPL loop1
 1300  STA (&80),Y
 1310  
 1340  \"…read the USER PORT and
 1350  \"…store as it goes posative
 1352  .loop2
 1360  LDA &FE60:BMI loop2
 1370  DEY:STA (&80),Y 
 1380  \"…decrement data counter
 1390  DEY:BNE get
 1391  \"…resync and get period counts
 1392  .sync
 1394  BIT &FE60:BPL sync
 1400  .loop3
 1410  \"…increment signal low counter
 1420  INC &404:BNE ok1
 1430  INC &405:BNE ok1
 1440  INC &406:BNE ok1:INC &407
 1450  .ok1
 1452  LDA &FE60:BMI loop3
 1460  .loop4
 1470  \"…increment signal high counter
 1480  INC &408:BNE ok2
 1490  INC &409:BNE ok2
 1500  INC &40A:BNE ok2:INC &40B
 1510  .ok2
 1512  LDA &FE60:BPL loop4 
 1520  \"…enable interupts before return
 1530  CLI:RTS
 1540  ]NEXT
 1550  ENDPROC