ECE 471 LAB 5 FALL 2008 PURPOSE: Practice with hooking up a device to the bus EXERCISE: For this lab you will hook a latch up to the data bus and "do something" with it to demonstrate proper operation. The something part is up to you. Something very simple is worth an 80. Something more elaborate will give you more points. Our boards supply a chip select line (active low) on the J1 connector above the LCD display (pin 40 labled "/CS" to the left). This line is active (i.e., low) whenever an address in the range $2000 to $3FFF is selected. If you do no further decoding, then your latch will respond to any address in this range. In addition to this /CS line, your latch must also involve E-clock and the R/W-bar line; i.e., you will clock data into the latch when /CS and R/W-bar are low (i.e., write operation) and on the falling edge of E-clock. The parts store has 74H174 (hex - 6 bit) and 74H175 (quad - 4 bit) latches. These both clock data in on the rising edge of the clock input, therefore the above condition (/CS low, R/W-bar low, and E-clock going low) must cause a rising edge on the latch's clock input. You do not need to latch all 8 bits, but do one at minimum. The data sheets for these and other devices can be obtained from http://www.fairchildsemi.com/ and other sites on Al Whitney's home page (http://www.eece.maine.edu/~whitney/). R/W-bar and the data lines are also available on the J1 connector. Don't forget to supply power to your latch chip and any logic chips used. To demonstrate proper operation, hook the latch up to something. Something simple is to hook it up to an LED and pull up resistor (properly sized) and make it blink. Note that the latches do not supply enough current with a high voltage (I_OH) to drive an LED directly; you will have to buffer them. However, they can sink much more current (I_OL is about 16 mA) and can therefore pull down on an LED in series with a resistor. Doing further address decoding (use at least two more address bits) will buy you 10 points. Using some HC11 feature that we haven't covered in lab yet will also buy you AT LEAST 10 points (e.g., pulse accumulator, SPI, writing to/reading internal EEPROM, booting to EEPROM code without using BUFFALO, etc.). This is your chance to go wild!