Task 9: Digital Data Formats: Parallel-to-Serial Conversion

Digital information may be represent in two distinct data formats -- "serial" and "parallel."  Within a computer, say, to maintain the most rapid internal communication rate, each information bit is in carried on a single connection (wire).  Thus, an informational word or bit configuration is carried on multiple connections in parallel (typically 4 parallel bits - a nibble, 8 parallel bits - a byte, 16 parallel bits, or 32 parallel bits).  On an external communication channel, however,  the informational word is carried in serial on a single connection (wire) as a time synchronous bit sequence.  To communicate between computers we must be able to convert data formats from parallel-to-serial and from serial-to-parallel.  Here we study how that conversion may be achieved.

1. Subtask 9a: An important single bit memory element.


First we need to learn about "D Flip Flops."  A D-FF is an very useful device for use in formatting digital signals.  First examine and then build the following Simulink configuration.  The inputs to the D-FF are labelled "D", "CLK" and "!CLR".  The outputs are labelled "Q" and "!Q".  Set your simulation parameters as follows: solver = fixed step/discrete; step = 1; and stop time = 99999999.  Start the simulation.  Notice that:

 
• When !CLR = 0, Q = 0 and !Q = 1, no matter what the other inputs may be -- i.e.,!CLR = 0 "clears" or "resets" the outputs.

 
• When !CLR = 1, Q becomes equal to D at the moment when CLK "rises" from 0 to 1.  At all other times Q is independent of D.

 
Thus, we see that Q remembers the value of D at the moment when CLK rises from zero to one!  Be sure that you believe this assertion.
 
2. Subtask 9b: A bit shift element.


To keep things as simple as possible, we will now use two D_FFs to convert two parallel bits into a time sequence of two bits.  Examine and then build the following Simulink configuration.  In this configuration you will see that the "word" [D1 D2} is saved as a parallel word [Q1 Q2] on rising CLK when the "control" switch is in the lower position.  However, when the "control" switch is in the upper position, you will observe that the bit in Q1 is shifted to Q2 on rising CLK and we have the basic element of a parallel-to-serial converter.  Set your simulation parameters as in Subtask 7a.
 

3. Subtask 9c: A shift register.


Build and test the following parallel-to-serial shift register configuration.  Set your simulation parameters as in Subtask 7a.
 

4. Subtask 9d: Digital encoding of an analog signal.
   

Finally lets put it all together.  Please build and study the following module which takes in an analog signal (perhaps an analog sample such as you obtained in Tasks 5 and 6) and converts it to a  serial or time sequenced digital signal.  Set your simulation parameters as in Subtask 7a.  To get the A-to-D converter "sg_adconv4" go Here

Task 10: A Study of Video Signals

In lecture we discussed various ways in which visual information may be displayed on a video display.  In this discussion, we review some of the important ideas involved in video processing such as scanning, pixels, spatial harmonics, luminance, horizontal and vertical ramp signals.  The general objective of this task is help you gain some insight into these and other video notions.

To this end, I would like you build and study the following three configurations:

• configuration 1: a test set up for non-localized spatial harmonics
• configuration 2: a test set up for localized spatial harmonics
• configuration 3: a test set up for arbitrary spatial patterns


The heart of these model systems is the MATHLAB function video129.  After you download this function and include it in the MATLAB search path, you can read its file header which explains in detail how the function works or you can review its operation at any time by writing "help video129" in the MATLAB Command Window.  Briefly, video129 is a simulation of a video display in which you can control and modify the display's characteristics.  See an example of a non localized spatial harmonic, an example of a localized spatial harmonic, an example of an arbitrary spatial pattern.  Important: After each invocation of video129, you must close the video display window.  If you do not close the display window, the next simulation will hang-up and you will get an error message.

The display is synchronized to the simulation clock by the input "time" and the input "horiz_res" sets the horizontal resolution.  In particular, the fixed horizontal dimension of the display is swept in a time 1/horiz_res so that the horizontal resolution increases inversely with the scan rate.  The input "line" sets the number of horizontal scans in a fixed vertical distance and, thus, is the direct measure of the vertical resolution.  Finally, the input "pixel" sets the luminance value at a given time instant and, thus, at a particular point on the display screen.  The pixel inputs should be chosen to vary between 0 (black) and 100 (white).  video129 returns (outputs) the horizontal and vertical signals which may be observed and compared with luminance signal on the muxed "Ramp Scope."
 

Task 10a: A Study of Non-localized Spatial Harmonics

 Build and study configuration 1: a test set up for non-localized spatial harmonics.
 
On the configuration, I have noted some initial values of various parameters to get you started, but I would like to strongly encourage you to experiment with other values.  Observe in particular how various non-localized spatial harmonics are generated by varying the frequency of the sine wave source.  Can you deduce a relationship between the temporal and spatial frequencies?  Check that you get the example cited above of a non localized spatial harmonic when you use the values I have noted on the configuration.
 

Task 10b: A Study of Localized Spatial Harmonics

•  Build and study configuration 2: a test set up for localized spatial harmonics.
 
On the configuration, I have noted some initial values of various parameters to get you started, but I would like to strongly encourage you to experiment with other values.  Observe in particular how various localized spatial harmonics are generated by varying the frequency of a sine wave source and the period and width of the pulse source.  Can you deduce a relationship between pulse period and width and pattern localization?  Check that you get the example cited above of a localized spatial harmonic when you use the values I have noted on the configuration.

Task 10c: A Study of Arbitrary Video Signals

 Build and study configuration 3: a test set up for arbitrary spatial patterns.
 
On the configuration, I have noted some initial values of various parameters to get you started, but I would like to strongly encourage you to experiment with other values.  Enter any function you may choose the "Fcn box" from the Nonlinear Memu  Check that you get the example cited above of an arbitrary spatial pattern when you enter the function 1 + sin(u)*cos(u/5)*sin(u/10)*cos(u/20).