EE 308 -- LAB 08, Part 2
Test of Memory and Port Expansion

Now that you have completed your wiring, you will test your work.

  1. Before adding chips to your board, check (and record) the resistance between VCC and GND. It should be at least several kOhms. If it is not this high, you have a mistake in your wiring.

  2. Before adding chips to your board, use a logic probe to check for power and ground. Connect your board to a 5 V supply. With a logic probe, check for a logic high at every pin which is supposed to be wired to VCC, and for a logic low at every pin which is supposed to be wired to GND. This will insure that you did not wire your power supplies backwards; such backwards wiring could destroy all your ICs.

  3. Program your Altera chip to act as the address demultiplexer and decoder.

  4. Turn off power, put in your three ICs and your resistor network, and turn power back on. Use a voltmeter to check your power supply voltage. If it is not 5 V, turn power off immediately -- you have a problem in your wiring.

  5. Connect Port B to LEDs, and make sure you can manipulate each bit of Port B individually. It is easy to do this in BUFFALO -- you do not need to write a program to do this.

  6. Program Port C as an output. Connect Port C to LEDs, and make sure you can manipulate each bit of Port C individually.

  7. Turn off power. Cut the trace on jumper J4 on the back of your board, and put your spare jumper on the two-pin header in the wire-wrap area. Have an instructor or TA help you with this. Last year, a few students cut the wrong trace. Connect the serial port to your computer, get into the Windows Terminal program, and turn on power. You should get the BUFFALO prompt. If you do, proceed. If not, you have a wiring error; get help troubleshooting your board.

  8. Fill all of the expanded memory with 0xAA's, then with 0x55's. (Use the BF command of BUFFALO.) If this works, then your memory is wired correctly.

  9. Connect wires from Port A of your 6821 to LEDs on your breadboard. Set up Port A for output. Do the following in BUFFALO: Change the value of 0xB001 to 0x00, change the value of 0xB000 to 0xFF, change the value of 0xB001 to 0x04. Then use Port A to turn on and off the LEDs on the breadboard. Do this in BUFFALO by changing the value of 0xB000. It this works, your board is wired correctly, and you now have 32 kbytes of RAM and two new ports. Congratulations!!!

Bill Rison, < >
Tue Mar 18 1997

© 1997, New Mexico Tech