di3547l1.txt
;******************************************************************************************
;
; LISTING 1 - SET PROGRAMMABLE CLOCK
;
; "Use a PC's parallel port to program a clock source," EDN, December 7, 2004, pg 102
;
;******************************************************************************************

unit$ = "Hz"
unit = 1
top:
CLS
PRINT "enter frequency units<"; unit$; ">";
IF unit$ = "Hz" THEN
        PRINT "khz,default";
ELSE
        PRINT "hz,default";
END IF
INPUT A$
IF A$ = "khz" THEN unit$ = "KHz": unit = 1000
IF A$ = "hz" THEN unit$ = "Hz": unit = 1
PRINT "enter frequency "; unit$;
INPUT f$
IF f$ = "" THEN END
c1 = VAL(f$) * unit
FOR I = 0 TO 15
        a3 = (2078 * 2 ^ I) / unit
        IF (a3 / (2 - 1023 / 1024)) > c1 / unit THEN
                b1 = I: I = 16
        END IF
NEXT I
a5 = 1024 * (2 - ((2 ^ b1) * 2078) / c1)
DAT& = b1 * 4096 + 4 * INT(a5 + .5) + 2
PRINT "coeff(dec)="; b1, INT(a5 + .5)
PRINT HEX$(b1 * 4096), HEX$(4 * INT(a5 + .5))
PRINT DAT&, HEX$(DAT&), "FREQ= "; (2 ^ b1) * (2078 / (2 - ((INT(a5 + .5) / 1024))))
P = &H378: N = 15
rep:
OUT P, &H1C   '  set enb
GOSUB serdrv
OUT P, &H1C   '  set enb
INPUT "eXit or continue<any other key>"; A$
IF A$ = "X" OR A$ = "x" THEN END
IF A$ = "C" THEN
  GOTO top
ELSE
  GOTO rep
END IF
'
serdrv:     'dat has data to send, c has number of bits to send
  FOR I = N TO 0 STEP -1   ' send passed data, n number of times
    OUT P, &H18            ' clear enb
    GOSUB DELAY
    IF (DAT& AND (2 ^ I)) <> 0 THEN
       OUT P, &H19
       GOSUB DELAY
       OUT P, &H1B             ' set dat
       PRINT "1";
       GOSUB DELAY
       OUT P, &H19             ' clear clk
    ELSE
       GOSUB DELAY
       OUT P, &H1A              ' set clk
       PRINT "0";
    END IF
    GOSUB DELAY
    OUT P, &H18                 ' clear dat(clk)
  NEXT I
  PRINT
RETURN
DELAY:
FOR j = 1 TO 100: NEXT j
RETURN