Motorola Axiom CMD11E1 Betriebsanweisung PDF herunterladen (Seite 31)

Chapter 3

Functions and bit manipulations

3.1 Objective

To become familiar with bit level operations and writing functions. This lab also

illustrates the use of random numbers for testing functions. Bit level operations

are used to control light emitting diodes connected to PORTA as well as for

monitoring external circuitry.

3.2 What you should do

You will be writing several functions in this laboratory exercise. You should

have only one ﬁle and you should add the new function at the end of your older

functions. Also, you will be adding items to the data section. You should not

delete earlier data items. Your main code will be changing. You should insert

your new main code before the older one, so that the most recent main code will

start immediately after the ORG statement. Try not to delete any code from your

ﬁle.

3.3 String outputs

In the last lab, we saw how to write a single byte as an ascii character. To write

a string, it is tedious to load A with one character at a time and then calling

OUTA each time. A better approach is to put all the characters in consecutive

memory locations and print them all in a loop. To do this, we need two pieces

of information, where to start and where to end. The common approach to such

situation is to specify where to start and use a special value, known as sentinel,

to indicate the end. Some of you may have used special values such as zero, one,

or 9999. It is entirely up to the programmer, but for character strings, the three

1 2 ... 26 27 28 29 30 31 32 33 34 35 36 ... 100 101

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Motorola Axiom CMD11E1 Betriebsanweisung Seite 31