Motorola Axiom CMD11E1 Uživatelská příručka stáhnout pdf (Strana 67)

5.5. WORKING WITH TABLES 67

;;; Add the code for lookup function here

Exercise: Type the above program and run it. Enter the following input and

explain what you see:

Exercise: Type the above program and run it. Enter the following input and

explain what you see: 123-34-1879.

Exercise: Modify the above program so that it accepts exactly 10 digits and

stops with an SWI after reading 10 characters. In other words, convert the main

loop into a counting loop. You should keep the count in the B register. Verify

your program with the input: 823--xx-34-1879.

5.5.3 Translations using tables

Some time we want to translate a value to another value. For example if the user

types the character 8, your program will receive the ascii code for the character.

You now will have to convert it to its value, viz 8. This is easy since you just have

to subtract $30. However, if the user enters data in HEX, then he would expect

the program to translate A and a to 10, B and b to 11 and so on. For problems of

this nature, we ﬁrst write down the translation table

value translation

$30 or ’0’ 0

$31 or ’1’ 1

$32 or ’2’ 2

etc. etc

$39 or ’9’ 9

$41 or ’A’ 10

$61 or ’a’ 10

$42 or ’B’ 11

$62 or ’b’ 11

etc. etc

In our assembly program we set up two tables. It is extremely important that the

two tables be ordered as follows: The table of values ﬁrst immediately followed

by the table of translations. For example, to perform the above translation, we

will write

1 2 ... 62 63 64 65 66 67 68 69 70 71 72 ... 100 101

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Motorola Axiom CMD11E1 Uživatelská příručka Strana 67