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Date: Wed, 08 Jan 1997 21:43:00 GMTServer: NCSA/1.4.2Content-type: text/html<html><head><title>CSE467 Laboratory Assignment #3</title></head><body bgcolor="#dddddd" text="#000000" link="#0000ee" vlink="501080" alink="ff0000"><h1>CSE467: Advanced Logic Design</h1><h3>Ted Kehl Fall 1996 </h3><hr><h3>Lab 3</h3><p><h3>Synario Hierarchy: Mixing Schematics and ABEL-HDL</h3><p><b>Distributed: Oct 18 <br> Schematics/Simulation Due: TA opt<br> (Constructed circuit Due: TA opt)<br> (Functional circuit Due: TA opt</b>)<hr><H3>Objectives</H3>After completing this lab you will know how to:<UL><LI>Use Synario to construct hierarchical circuit schematics<LI>Include ABEL programs in schematics as devices<LI>Debug synchronous designs using simulation<!--<LI>Program PLDs<LI>Debug physical circuits--></UL>From now on, you will be working (sometimes rather loosely) in teamsof four. The first part of this assignment has you follow a tutorialwhere you should work in groups of two. In the second part you aregiven a circuit that divides naturally into two parts, each of whichcan be solved individually by half the team and then linked togetherto form a complete solution.<p><b>Note:</b> Although the tutorial is rather complete, you may need tolook in the Synario manuals in the lab to answer questions you mayhave or to use more advanced features.<H3>I. Tutorial: Topdown Design Using ABEL with Schematics </H3>This tutorial has you design a counter that counts 1,2,3,..,N where Nis an input to the counter. This counter is composed of two componentmodules, a simple counter and a comparator. The comparator comparesthe endcount to the current count value and causes the counter torestart.<P><b>Note:</b> You will not be following the tutorial exactly, but wewill let you know where things diverge.<H3>II. Design Problem: Serial Communication</H3>You are to construct a sequential circuit that interfaces a simplekeypad to an LCD screen. Characters to be printed on the LCD screenwill be keyed in using two key presses: one for the first 4-bit nibbleof the character's code and one for the second 4-bit nibble. Forexample, to print an "A" one would key in a "4" and a "1".The circuit you design will communicate values from the keypad to theLCD display using your solution to Homework 2, Problem 6, whichpresented a method for bit-serial communication. You will start bydesigning and simulating your circuit in Synario. In the next weeks,you will program parts of your circuit into PLDs, plug them in and getthe circuit work.<P> The figure below shows the components of your system:<p>(Figure 1)<h4>The Keypad</h4>The first half of the circuit takes values entered on the keypad andsends them serially to the second half of the circuit.<p>The keypad has nine wires: one for each column (5 through 8), one foreach row (1 through 4), and a common wire (9) to be connected toground (this is the common connection for all the switches). When akey is pressed the corresponding column and row wires are connected tothe common signal (see the figure below). Therefore, the keypad iscalled a 2-of-8, 2 of the 8 wires will be active low when a key ispressed, the others are pulled high through resistor connections to5v.<p><img src="debounce.jpeg"><p><P>The first part of the task is to convert the 2-of-8-bit value from thekeypad wires into a 4-bit value plus a "ready" bit. The 4-bit valueencodes the key pressed into a binary number (0000 to 1101 for 0through 9 followed by A, B, C, and D; 1110 for *; and 1111 for #).The ready bit is synchronized to the clock and is asserted high forone cycle indicating that a key has been pressed. The rest of yourcircuit will collect two 4-bit values and send them serially accordingto our protocal across the link to the LCD display circuit. Also, youwill need to latch (i.e., store in a register) the first key pressedwhile you wait for the second so it might be a good idea to just latchboth (this can be done with one or two `373s). <H4>The LCD Screen</H4>The second half of the circuit receives the data sent bit-seriallyfrom the keypad and displays the value on the LCD screen.<P>The display you will be using has a very straightforward interface.It takes instructions or data depending on the value of the RS wire.The table below shows the instructions you will be using. Fourinstructions are required to initialize the display for theconfiguration we require (a 1 line by 16 character display). Theseare shown in the first four lines of the table. So your control logicmust be sure to issue these instructions whenever it is reset.<P>After reset, all you need to do is write characters to the display(the fifth line in the table). These will be displayed immediately bythe display unit. Finally, you will hit the reset switch again andstart entering a new number. You can find the character codes in thedisplay documentation.<pre>Operation RS R/W DB7...DB0Clear Display 0 0 0000 0001Function Set 0 0 0011 00**Display ON 0 0 0000 1100Entry Mode Set 0 0 0000 0110Write Character 1 0 DDDD DDDDBackspace 0 0 0001 00**Return Home 0 0 0000 000*Read Character 1 1 DDDD DDDD</pre>The timing constraints that must be satisfied when writing informationinto the display are quite straightforward. Basically, the displaysamples the RS line on the rising edge of the enable signal (E) and DBlines on the falling edge of E. To keep things simple, the set up andhold time for RS should be one cycle before and after the rising edgeof E, respectively. Similarly for the DB lines and the falling edgeof E. The only other timing information of importance is to allow upto 1.6ms for the display to actually clear (the internal controllerstakes some time to actually go and enter 0s in the internal memory ofthe display unit).<P> Since your project does not need to perform read operations, theR/W control line can be tied directly to GND. For normal characterwrite operations, the RS signal should be 1. To execute a command,the RS signal should be 0. The easiest way to perform a write is byasserting the enable signal (E) for one clock cycle during which RSand data are both stable. You must ensure that the number code isstable while this is happening. This shouldn't be a problem as a keypress takes a lot longer than your circuit will need. However, youshould ensure that RS is stable for a cycle before and after the writeoperation is performed. You will need to do this in your controller'sfinite state machine. Since the Enable signal is used to clock datainto the display, it should be hazard-free (no spurious glitches).The easiest way to ensure this is to make it a direct output of aflip-flop in the PLD.<h4>Details, Details, Details...</h4> Part of designing a circuit to solve a problem is defining what theproblem is. Most problem descriptions are hazy, incomplete andambiguous. One of the tasks of when designing is to turn such adescription into a precise specification. Before you begin to design,ask yourself what is missing and <b>write down</b> as precise aspecification as you can. You may save yourself a lot of work in theend. Document both parts of your circuit design (preferably usingWord), specifying how the pieces will interact and how you will solveeach part. Include this documentation in your Synario project andhand it in with your schematics.<P><B>NOTES:</B><ol><LI> Don't forget to provide a reset input to both halves of yourcircuit.<LI> You will have to figure out how to signal the beginning of datato separate it from idle time.<LI> Decide on a good speed for your clock which suits the LCDdisplay. You might as well simulate at your proposed clock speed.(Hint: it should be relatively slow.)</ol><h4>Entering and Simulating your Design</h4>Divide each half of your design into reasonably-sized components, suchas registers and counters and combinational logic that can fit in asingle PLD. Draw a top-level schematic for your design, including thecomponents that you need. (Work with your TA if you are not sure howto define this hierarchy.) Use ABEL to specify both your sequential(e.g. counters) and combinational (e.g. code converter) components.You will find some useful chip definitions in the t:\cse467 directory.You can use these in your schematics by first importing them, thencreating the matching symbol (the tutorial covers this). You may wantto do this for other standard chips although you can use PLDs for mosteverything.<P> You should simulate your designs separately as best you can, andthen combine the two projects using a new top-level schematic.(Start a new project then import the pieces of the two projects.)To simulate the complete design, you will need to provide the keypadstimulus, which is easy to do on eight inputs, and you will need tocheck that the commands to the LCD display are correct. For now, youwill just have to check this by hand.<P> Here is an example of a Verilog test fixture which uses oneprocess to set the "test vectors" and a separate process to generate afree-running clock:<pre>// Consistently set the timescale (1 ns) and the precision (1 ns)// Should be set in the top level file (here) because it may be// defaulted differently in separate submodules`timescale 1 ns/1 ns// Declare the toplevel module namemodule t;// Include the interface to the schematic and ABEL source`include "keypad.tfi"// Initialize the inputs. Then form input stimuli.// Because of the way the clock is structured,// it is safe to change inputs at times: 0, 100, 200, 300, etc.initialbegin CLK = 0; RESET = 1; {R0,R1,R2,R3} = 0; {C0,C1,C2,C3} = 0; #200 RESET = 0; #1000 {R0,R1,R2,R3} = {1,0,0,0}; {C0,C1,C2,C3} = {0,1,0,0}; #300 {R0,R1,R2,R3} = {0,0,0,0}; {C0,C1,C2,C3} = {0,0,0,0}; #300 {R0,R1,R2,R3} = {0,0,1,0}; {C0,C1,C2,C3} = {0,0,0,1}; #300 {R0,R1,R2,R3} = {0,0,0,0}; {C0,C1,C2,C3} = {0,0,0,0};end// This clock has a period of 100 ns. The rising edges occur at// times 50, 150, 250, etc.always begin #50 CLK = 1; #50 CLK = 0;endendmodule</pre><H4>Extra Credit</H4>Many other options can be incorporated into this circuit. Forexample, you may want to implement a back-space function using thecode "A0" (10100000).<H2>Turn in (Due: TA opt)</H2>(Turn in the design in one piece.)<Ol><LI>Design documentation<LI>Printout of Schematics<LI>Printout of ABEL modules<LI>Printout of simulation waveform <b>annotated</n> to show thatcircuit is working correctly.</OL></body><address><hr>ted@cs.washington.edu</address><p></html>⌨️ 快捷键说明
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