quote of the day

"My stack runneth over." - Jordan Melzer

notes on labs, etc..

742LS44 = Dual 4-bit 3-state noninverting buffer/line driver.
     +----------+
/1OE |1  +--+ 20| VCC
 1A1 |2       19| /2OE
 2Y4 |3       18| 1Y1
 1A2 |4       17| 2A4
 2Y3 |5  74   16| 1Y2
 1A3 |6  LS   15| 2A3
 2Y2 |7  244  14| 1Y3
 1A4 |8       13| 2A2
 2Y1 |9       12| 1Y4
 GND |10      11| 2A1
     +----------+
note that in the above: A means input and Y means output.

try to wire boards neatly; easier to debug.

meaningful well organized colour schemes; meaningful selection of colours.

understand exactly what the circuit does and how it works, e.g. understand how to test parts of the circuit and isolate a problem.

lab2 introduced basics of wiring up a circuit; lab3 introduces other issues such as timing.

74LS138 = 1 of 8 inverting decoder/demultiplexer.

     +----------+            +-----------------------------------------+
  S0 |1  +--+ 16| VCC        |EN1|/EN2|/EN3| S2| S1| S0|/Y0|/Y1|...|/Y7|
  S1 |2       15| /Y0        |---+----+----+---+---+---+---+---+---+---|
  S2 |3       14| /Y1        | 0 | X  |  X | X | X | X | 1 | 1 | 1 | 1 |
/EN3 |4   74  13| /Y2        | 1 | 1  |  X | X | X | X | 1 | 1 | 1 | 1 |
/EN2 |5   LS  12| /Y3        | 1 | 0  |  1 | X | X | X | 1 | 1 | 1 | 1 |
 EN1 |6  138  11| /Y4        | 1 | 0  |  0 | 0 | 0 | 0 | 0 | 1 | 1 | 1 |
 /Y7 |7       10| /Y5        | 1 | 0  |  0 | 0 | 0 | 1 | 1 | 0 | 1 | 1 |
 GND |8        9| /Y6        | 1 | 0  |  0 | . | . | . | 1 | 1 | . | 1 |
     +----------+            | 1 | 0  |  0 | 1 | 1 | 1 | 1 | 1 | 1 | 0 |
                             +-----------------------------------------+

74LS373 = 8 bit 3state transparent latch.

    +----------+             +---------------+
/OE |1  +--+ 20| VCC         |/OE| LE| D | Q |
 Q1 |2       19| Q8          |---+---+---+---|
 D1 |3       18| D8          | 1 | X | X | Z |
 D2 |4       17| D7          | 0 | 0 | X | - |
 Q2 |5   74  16| Q7          | 0 | 1 | 0 | 0 |
 Q3 |6   LS  15| Q6          | 0 | 1 | 1 | 1 |
 D3 |7  373  14| D6          +---------------+
 D4 |8       13| D5
 Q4 |9       12| Q5
GND |10      11| LE
    +----------+

Today's lecture: Sleep and the sands of time

usleep.c, a simple userspace program for use in shell scripts

why timing is important

the sands of time

long time delays