CSC270 Homework 7 2011
--D. Thiebaut 09:24, 6 April 2011 (EDT)
This assignment is due on Wednesday, April 15th (apparently a day for cake...)
Problem #1
Design a 3-LED sequencer implemented with a 6811, and draw the full schematics (as we did in the last lab). This sequencer behaves very similarly to sequencers you designed with a flipflops before Spring break. We will label one LED the green LED, another one the yellow LED, and the last one the red LED.
Show the 6811 assembly language program that will activate the LEDs in the following pattern: Green is ON for 1 second, then Yellow turns on for a second, then Red comes on for a second. And the cycle starts over with Green coming on. In other word, create a 3-state sequencer where each LED is ON in one state only. But now your sequencer is controlled by a program.
Assume that we decided that Green should stay on for 2 seconds, Yellow for 1 second, and Red for 5 seconds, comment on the difficulty/complexity of modifying the sequencer if the sequencer is implemented with flipflops, compared to the difficulty/complexity if the sequencer is implemented with a 6811.
- Note: You have two options for this design. One is to use 3 different outputs (if possible) from the 7442, and connect them to the 3 different flipflops. One is to use the same output from the 7442 and connect it to the 3 different clock inputs of the 3 flipflops. In this case you can use different data bits for the different flipflops...
Problem #2
Instead of wiring the 7442 as you did in the lab on 4/4/11, when you were implementing the 1-bit Output Port, assume that you had wired the 7442 to the 6811 in the following way:
- A3 of the 7442 is connected to A13 of the 6811
- A2 of the 7442 is connected to A14 of the 6811
- A1 of the 7442 is connected to A15 of the 6811
- A0 of the 7442 is connected directly to E of the 6811 (no inverter!)
- Ouput 3 of the 7442 (Pin 4) is connected to the clock input of the 74LS74 flipflop.
Will this design work? In other words, will the LSB of Acca get stored in the flipflop when the processor execute
STAA 9000
Why, or why not? Explain thoroughly why it will or will not work.
Be careful, this is tricky!
