EE 308 -- LAB 08, Part 2
Test of Memory and Port Expansion
Now that you have completed your wiring, you will test your work.
- 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.
- 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.
- Program your Altera chip to act as the address demultiplexer and
- 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.
- 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.
- Program Port C as an output. Connect Port C to LEDs, and make sure you
can manipulate each bit of Port C individually.
- 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.
- 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
- 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.
Tue Mar 18 1997
© 1997, New Mexico Tech