CSC270  Homework #9

Part 1: Mystery Program

Translate the following program into assembly and then describe what it does in English.
It starts at address 0010: CE C1 68 86 7E BD 00 3B CE C1 58 86 1D BD 00 3B CE C1 48 86 15 BD 00 3B CE C1 38 86 11 BD 00 3B CE C1 28 86 06 BD 00 3B 7E 00 10 C6 08 A7 00 08 46 5A C1 00 26 F7 39

Part 2: The traffic light sequencer revisited.

Figure 1: Two-bit port to be modified.

Figure 1 shows the main components of the two-bit output port setup as we used it in lab. (The 6800, a decoder, two bidirectional buffers controlled by RE-bar, two D-flipflops, the outputs of which are connected to two LEDs). Redraw the 2-bit port that you created in lab11, using 2 flip-flops. Redraw it in the diagram above, then modify it by adding a third flipflop connected to a third LED. Label the 3 LEDs Green, Yellow, and Red.

Write a program for the 6800 to activate the green, yellow and red LEDs in the following pattern:

• The green LED is first turned on for 4/10th of a second, then turned off.

• The yellow LED is then turned on for 1/10th of a second, then turned off.

• The red LED follows by being turned on for 2/10th of a second, then turned off.

• The pattern repeats and the green LED is turned back on.