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EE395 -  Microprocessor Laboratory

Computer Construction Project and Experiments

Experiment 2:  Demonstrating Familiarity with the SBC

Although you may have written much of the software that follows in the microprocessor lecture course, you now have the opportunity to test the software in its native environment. Previously you could only test software using a crossemulator on a PC. It is therefore worthwhile to perform the experiments below in order to acquire greater familiarity with the 68000 line of microprocessors.

Finding the Position of a Letter in a String

The students should use the Antonakos’s cross-assembler to write a program for finding the position of the letter ’x’ in any one of the following strings:

1.  I have never seen a better experiment.

2.  This is an overly short and dull experiment.

3.  This is a fairly simple but exciting experiment.

4.  This is an interesting though not long experiment.

5.  Hmm, this isn’t as dull as all that, as experiments go.

This short program can then be downloaded into the microprocessor and tested.

The string should be stored in the RAM that immediately follows the required program. This is done using the DC.B directive. The position of the letter ’x’ in the string should be displayed on the LEDs of the parallel output port.

Moving a string in RAM

Write and debug a program for moving the string of data from the previous part to a higher memory location (of your choice). The A0 register is initialized to point to the beginning of the data source, the A1 register is initialized to point to the beginning of the data destination, and the D1 register is initialized to contain the count. This program will pick up the data one byte at a time and deposit it one byte at a time. When the (16 bit) D1 register is down to zero the transfer is complete. The program should first fill the destination area with 0FFHs so that the success of the move will be perfectly clear.

Even though your string is very short your software must be prepared to transfer up to 64 kbytes of data.