Motorola Axiom CMD11E1 Guía de usuario descargar pdf (Pagina 98)

98 CHAPTER 9. ANALOG TO DIGITAL CONVERSION

4. Take a reading (this is easy!)

LDAA ADR1

5. Convert it to decivolts by multiplying by 50 and then dividing by 255

LDAB #50

MUL

LDX #255

IDIV

The quotient as a result of division is in the X register. This is an awkward

destination as most of the functions expect the value on the A register. We

transfer from X to A in two steps.. ﬁrst from X to D. Now the result is in

the [A—B] pair and since the value is less than 255 (the value is between 0

and 50), the result is in the B register. We transfer the value from B to A.

XGDX * D <-> X

TBA * B -> A

6. Print the value in decimal We can now convert the data to BCD format and

then print the left and the right digit.

JSR HEX2BCD

PSHA *SAVE IT FOR LATER USE

JSR OUTLHLF

LDAA #’.

JSR OUTA

PULA *GET THE SAVED VALUE

JSR OUTRHLF

JSR OUTCRLF

The code to convert to BCD was discussed in an earlier section and is

produced here for reference:

HEX2BCD

PSHB

1 2 ... 93 94 95 96 97 98 99 100 101

Sin comentarios

Motorola Axiom CMD11E1 Guía de usuario Pagina 98