CE121L - Microprocessor System Design
Laboratory 2
Week of January 13, 1996

For this lab, you will hook up the HC11 clock, reset, and address/data latch. Next week, you'll hook up the address decoding, EEPROM and SRAM. The basic components will be the HC11, RS232 level converter, SRAM, EEPROM (you'll be taking this one in and out quite a bit), decoder, 2 latches, D/A converter, and crystal or oscillator.

Prelab

1. Read your HC11 manual. In particular, read chapter 2 very carefully, chapter 3, and the parts of chapter 5 that deal with resets.
2. Decide on wire colors for power, ground, and the three buses (address, data, and control). Stick to your color scheme, and add additional colors as necessary. You may wish to use additional colors (eventually) for analog signals. Write it up in your lab notebook, of course.
3. Design an approximate layout of chips for your board. Run data and address busses along the long axis, perpendicular to the chips. Place the D/A chip as far from the digital and power circuits as possible. Place the RS232 level converter as far away from everything else as possible. (Yes, these are all conflicting goals!) You may wish to place the EEPROM at the edge because you will be removing and inserting it frequently -- in the past, some groups have used a ZIF (zero insertion force) socket for the EEPROM, something that's easy to find at Fry's. Refer to your parts kit or data sheets to find how much room to allow for your devices. Only the two memories will require a large number of address lines. It is always a good idea to keep your analog parts as far away from your digital parts as possible, and to take their power supply directly from your main power and ground pins. Show your diagram to the TA early in the lab period.
4. DIP switches will be available. Decide how to hook up one to the reset line.
5. Carefully read about each pin of the HC11 and decide whether or not it is an input pin. All input pins must be driven. They must either be tied to some signal, such as the clock or the reset button, or they must be tied to power or ground as appropriate. Decide which is appropriate for each one. Your system will not work if some of these are allowed to float.
6. Start a detailed wiring diagram in your lab notebook -- you may wish to use Logic Works or a a similar editor, or just graph paper and a straight edge.

As mentioned in the initial laboratory handout, prelab must be completed in your lab notebook before coming to lab. You can affix your diagrams with tape to your lab notebook.

Laboratory

1. We will be using a 7805 power regulator in lab. The 05 refers to 5V output (at 1.0 A, maximum), while the 78 is the series of power regulator. Power regulators have three pins: input (pin 1), ground (the center pin), and output. The 7805 is rated for inputs between 7V and 35V, so you will be able to run your project from a 9V battery at home if you desire. Before putting in your power regulator, check its characteristics using the scope and the power supply. Plot its output voltage over a range of positive input voltages to ensure it's working.
2. Solder and connect pins for clipping power supply power and ground to, and solder these to the power regulator. Add in several wirewrap posts, connected together, and solder these to the 7805 output and to ground. These will be the main power source pins for your project. You may wish to practice solder on a few holes of your board before using the real parts. Once the soldering iron is heated up, rub it on the damp sponge, and put a little solder on the iron. Then, place the iron so it touches the appropriate hole and the wire coming through to heat things up. Touch the solder to the opposite side of the wire (that is, do not melt solder with the soldering iron, but with the hot wire). Be sure to use protective eyewear, and avoid breathing the solder fumes.
3. Place your HC11 socket on the board, as well as the sockets for all the other chips, to get a feel for your layout.
4. Solder in one or two pins from each of the 24-pin SIP strips. Make sure the strips are correctly spaced! Solder in your other sockets as well to avoid having to solder after wire-wrapping.
5. Solder in the bypass capacitors and the crystal circuit (be sure to check the polarity of the electrolytic capacitors!). Connect the crystal circuit to 2 WW pins, which you can then wirewrap to the HC11. This way, you will be able to easily switch from the crystal to the function generator as a clock source, and allowing you to insert a single-step circuit using a flip-flop and a switch. Alternative: use a wirewrap socket and an oscillator (available in your locker). This will be simpler and less prone to error.
6. Wirewrap the HC11's power and ground, and other input signals so we can try setting and unsetting the reset pin. For the time being, do not worry about tying bus and parallel I/O inputs to power and ground, but make sure all the control inputs (ie, the pins on the left in diagram 2-23) are tied correctly.
7. We are going to examine the behavior of the circuit during a reset using the scope and the function generator. Produce a 5V, square wave on the order of 10KHz and apply it to the reset pin. Use the scope to examine all outputs from the HC11 to build up an overview of what the processor does on a reset. Make a diagram of all these signals in your lab notebook.
8. Connect the address/data latch and check its function with the continuous reset test.