EE 308 - LAB 11
Setup for Additional Memory, Ports, and D/A Converter
In this lab you will put the necessary hardware on your board to enable
you to add additional memory, ports, and a D/A converter to your HC12.
You will use an 84-pin Altera chip for address demultiplexing, and to
build additional ports. Two 32-KB static RAM chips will provide your
additional memory. A D/A converter will give your board the ability to
provide two analog outputs. Your Altera chip uses a 3.5 V power supply,
so you will add a 3.5 V regulator to provide power for the Altera chip.
The HC12 uses ports A and B to provide the multiplexed address and data bus.
When you use the HC12 in expanded mode, you are no longer able to use these
ports. To compensate for this we will use the Altera chip to provide two
eight-bit I/O ports.
The attached schematic shows how the parts
are connected. The layout diagram shows how you
should put the parts on your board. The wiring
list shows which pins to connect.
- Lay out the parts provided as shown in the layout diagram. Be sure
to place the parts as shown - there is very little room for adding parts
to the HC12 EVB, so unless you add the parts as shown, you may not have
enough room to put on everything you need.
- For the large parts (IC sockets and headers) solder two pins on
opposing corners to hold the parts in place.
- For the power and ground headers, solder all pins.
- Solder the resistors, capacitors, and voltage regulator to your board.
Make sure the leads are straight, and trim them to about the same length as
the leads on the wire wrap sockets.
- Place wire-wrap labels on the four wire wrap sockets, and the expansion
- To wrap a wire onto a pin, strip about 3/4" to 1" of
insulation from one end of the wire. Wrap that end of the wire onto the
pin, making sure a small amount (about 1/2 turn) of insulated wire is
wrapped around the pin. Cut the wire to the necessary length to reach
the next pin, strip insulation from the free end, and wrap that end.
- Use different colors of wires for different functions.
It is common practice to use red for power and green for ground.
You might use blue for AD0-AD15, yellow for A1-A15, white for control lines,
and black for expansion ports.
- Start with one group of pins (e.g., address), and do all wiring
for that group before moving on to the next group. I did the wiring in this
- Power and Ground
- Control Lines
- Expansion ports
- Wire long wires first, short wires last.
- Route wires around the outside of the sockets.
- Do not daisy-chain power and ground lines from one component to
another. Instead, fan out from a power or ground pin to the components.
- Take a highlighter pin and highlight the wires you have run on your
wiring list as you wire them.
- After all the wiring is done, take an ohmmeter and check the
continuity of all wires on the wiring list. (Check continuity after
you've run the first few wires just to make sure your wiring technique
- Next week's lab will use the D/A converter. Make sure all wiring for
this is done by next week.
- If you can't finish all the wiring by next week, try to have all power
and ground wiring done, AD0-15 from the HC12 to the Altera chip, and the
expansion wiring (Altera chip to header J1). This will allow you to begin
testing your wiring next week.
- In two weeks, all wiring must be completed. We will finish the memory
expansion in that lab.