Motorola Axiom CMD11E1 Guia do Utilizador descarregar pdf (Página 8)

8 CHAPTER 1. INTRODUCTION TO HC11

CTRL-A Quit.

BF <addr1> <addr2> [<data>] Block fill.

BR [-][<addr>] Set up breakpoint table.

...

1.2.2 Looking at memory

To see what is stored in the HC11 memory, we use the memory dump command.

The instruction for dumping memory is MD. Let us look at what is present in

locations E000 to E3FF. At the prompt, enter the command MD E000 E3FF. You

should see:

>MD E000 E03F

E000 CE 10 0A 1F 00 01 03 7E B6 00 86 93 B7 10 39 86 9

E010 00 B7 10 24 8E 00 68 BD E3 40 CE 00 4A DF A7 86 $ h @ J

E020 D0 97 A6 CC 3F 0D DD 69 BD E1 9A 7F 00 A9 7C 00 ? i

E030 A9 7F 00 AB B6 10 3C 84 20 27 35 86 03 B7 98 00 < ’5

Each line of output consists of three parts. First there is the memory address,

for example E020. This is followed by 16 bytes of data. These are contents

of 16 locations starting from the address. For example, in the above example,

memory location E020 contains D0, location E021 contains 97 etc. Recall that all

numbers are in hex. After the 16 bytes come 16 characters. Each of the bytes is

interpreted as an ASCII code and the character that the code represents is shown.

Non printable and non-ascii characters are shown as a space.

Exercise

1. Look up the ascii code for the letter J. Can you locate it in the memory

dump shown above?

2. Determine the contents of the locations FFD0 to FFFF. Write down the con-

tents in your lab notebook. You will need these values later in the course.

1.2.3 Modifying memory

Now that you know what is in the memory, let us try to modify the contents of

the memory. Let us store the following values in locations starting from C100: B6,

D0, 00, BB. To modify memory, we use Memory modify command, MM. When you

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Motorola Axiom CMD11E1 Guia do Utilizador Página 8