SP9841 datasheet(31/32 Pages) SIPEX

31 / 32 page

297

Figure 16. Microsoft qbasic Program to Load Evaluation Board with Desired Codes.

SP9841.BAS

'This program accepts an address (1 through 8) and data (0 through 255)

'in decimal and sends them to the DAC.

Addresses 1 through 8 will

'correspond to converters A through H respectively.

The appropriate

'output will be:

Vout-(data/128)*VREF volts.

'We found that for our IBM PC/AT the LPT1 port address was 378H (Data

'Register 378H and control register 37AH) while for our IBM PC/XT the

'LPT1 port address was 3BCH (Data Register #BCH and control register 3BEH).

DIM lsb AS INTEGER

DIM msb AS INTEGER

DIM datareg AS INTEGER

DIM contrlreg AS INTEGER

DIM n AS INTEGER

CLS

INPUT "Enter type of PC, AT or XT: ", type$

IN UCASE$(type$) = "AT" OR UCASE$(type$) = "XT" THEN

EXIT DO

ELSE PRINT "Please enter either AT or XT.": PRINT

END IF

LOOP

IF UCASE$(type$) = "AT" THEN datareg = &H378: cntrlreg = &H37A

IF UCASE$(type$) = "XT" THEN datareg = &H3BC: cntrlreg = &H3BE

CLS

n=0

WHILE n=0

test$ =""

INPUT "Enter Address (1 through 8): ", lsb

IF lsb < 1 or lsb> 8 THEN test$ = "false"

IF test$ = "false" THEN PRINT "Please enter a valid address.": PRINT

LOOP UNTIL test$ <> "false"

test$ = ""

INPUT

"Enter Data (0 through 255 in decimal): ", msb

IF msb < 0 or msb > 255 THEN test$ = "false"

IF test$ = "false" THEN PRINT "Please enter valid data.": PRINT

LOOP UNTIL test$ <> "false"

OUT cntrlreg, $H3

'set both latch clocks low

OUT datareg, &H0 + msb

'send most significant byte to port

OUT cntrlreg, &H2

'clock U1

OUT datareg, &H0 + lsb

'send least significant byte to port

OUT cntrlreg, &H0

'clock U2

OUT cntrlreg, &H4

'enable U7, set U1 & U2 to serial out mode

PRINT :

PRINT "Strike spacebar to enter new data or Q to quit."

X$ = INKEY$

IF UCASE$(X$) = "Q" THEN n=1

LOOP UNTIL X$ = " " OR UCASE$(X$) = "Q"

LOOP

END

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