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40 CHAPTER 3. FUNCTIONS AND BIT MANIPULATIONS

JSR RAND

JSR PRBINARY

SWI

;;; INSERT YOUR CODE FOR PRBINARY HERE

;;; INSERT YOUR CODE FOR RAND HERE

ORG $D000

;;; INSERT ALL YOUR DATA (FCB, FCC, RMB etc.) here

ABOUTME FCC / INFORMATION ABOUT YOU /

FCB 4

SEED FCB 0

;;;;;;;;;;;;;;;;;;;;;;;end of code ;;;;;;;;;;;;;;;;;;;;;;;;

3.6 Setting bits

We will now write a function that will set a particular bit in some memory location.

The function should modify the value in the memory in such a way that it only

aﬀects the speciﬁc bit without changing any other bit. For deﬁniteness, we will

set bit #4 in memory location $00. Recall that the bits are numbered right to left

starting with bit #0. To set a bit, we use the ORA instruction. Write the following

program, and test it by repeating the call to $C100 from the BUFFALO prompt.

;;;;;;;;;;;;;;;;;;;;;;;start of code ;;;;;;;;;;;;;;;;;;;;;;;;

;; Insert standard buffalo equates here

ORG $C100

JSR OUTCRLF *NEED THIS FOR OUTPUTS TO LINE UP!

JSR RAND

STAA $00

JSR PRBINARY *PRINT BEFORE

JSR SETBIT4

LDAA $00

JSR PRBINARY *PRINT AFTER

SWI

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

; Function: SETBIT4

; Purpose: SETS bit #4 in memory location $00

; Registers modified none

;

1 2 ... 35 36 37 38 39 40 41 42 43 44 45 ... 100 101

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Motorola Axiom CMD11E1 Guía de usuario Pagina 40