1 Prelab

1. Wire wrap the two 7-segment displays along with the pin header needed on a perf board (as shown in Figure 2). schematics of MAN74 7-segment display.

   Figure 2: Dip switches

   
   What is shown in the figure is only a suggestion as a start and you may need to do some modifications. For example, rather than having the ground pins at the top and bottom of the board, you may put those pins seperately on the side. So rather than having 10 pins at the top and the bottom, you will have 8 pins on the top, 8 pins on the bottom and 4 pins on the side. This will give you more flexibility in connecting the board.

2. Fill in the truth table for the BCD-to-7-segment decoder shown in Table 1, e.g., if the input is 0011, LEDs a,b,c,d and g should be on while LEDs f and e will be off (see Figure 1). For inputs 0xA through 0xF, naturally they don't correspond to any number in the range 0-9, therefore output the corresponding hex value instead, i.e., for 0xA the display should show the letter A.
   

   Table 1: Truth table for 7-segment-display decoder (1 means that LED is on and 0 means off).

   Digit	Binary	a	b	c	d	e	f	g
   0
   1
   2
   3	0011	1	1	1	1	0	0	1
   4
   5
   6
   7
   8
   9
   A
   B
   C
   D
   E
   F

   
   
3. A simple computer has several main blocks, e.g.,
   • Arithmetic logic unit (ALU): performs arithmetic operations on numbers.
   • Memory: where the program is stored.
   • Multiplexers: select which piece of information to be passed on.
   • Decoders: to determine, based on the input, whether to read from memory or input/output lines.
   • Computer control unit: outputs the control signals that direct the operation of the rest of the computer.

   Even though we are not building a computer, this information gives you some prospective on the different components that you will be building and what they may be used for.

   In this labs lab we will focus on the multiplexer that chooses either a program address (PROG_ADDR), program counter (PC), memory address register (MAR) or index register X (X). These signals are used to determine the information required to enter the arithmetic logic unit component of the computer.

   1. Design a multiplexer with MEM_SEL as the select signal, PROG_ADDR, PC, MAR and X as 8-bit input signals.
   2. Design a Verilog program to implement this multiplexer.