Chapter 3. Basic Concepts
3.5 Exercises
1. Practice writing the following numbers:
a) Decimal number 123 as a sized 8-bit number in binary. Use _ for readability.
b) A 16-bit hexadecimal unknown number with all x’s.
c) A 4-bit negative 2 in decimal. Write the 2’s complement form for this number.
d) An unsized hex number 1234.
my answer:
a) 123 = 8’b0111_1011
b) 16’hx
c) -4’d2=4’b1110
d) 32‘h1234
2. Are the following legal strings? If not, write the correct strings.
a) “This is a string displaying the % sign”
b) “out=in1+in2”
c) “Please ring a bell \007”
d) “This is a backslash \ character\n”
my answer:
a) “This is a string displaying the %% sign”
b) right
c) right
d) “This is a backslash \\ character”
3. Are these legal identifiers ?
a) system1
b) 1reg
c) $latch
d) exec$
my answer:
a) right
4. Declare the following variables in Verilog:
a) An 8-bit vector net called a_in.
b) A 32-bit storage register called address. Bit 31 must be the most significant bit. Set the value of the register to a 32-bit decimal number equal to 3.
c) An integer called cout.
d) A time variable called snap_shot.
e) An array called delays. Array contains 20 elements of the type integer.
f) A memory MEM containing 256 words of 64 bits each.
g) A parameter cache_size equal to 512.
my answer:
a) wire [7:0] a_in;
b) reg [31:0] address=32’d3;
c) integer cout;
d) time snap_shot;
e) integer delays [0:19];
f) reg [63:0] MEM [0:255];
g) parameter cache_size=512;
5. What would be the output/effect of the following statements ?
a) latch = 4’d12;
$display(“The current value of latch = %b\n”, latch);
b) in_reg=3’d2;
$monitor($time, “ In register value = %b\n”, in_reg[2:0]);
c) `define MEM_SIZE 1024
$display(“ The maximum memory size is %h”, `MEM_SIZE);
my answer:
a) The current value of latch =4’b1100
b) 0 In register value = 3’b010
c) The maximum memory size is ‘h400
Reference
Smair Palnitkar, <Verilog HDL: A Guide to Digital Design and Synthesis (2nd) >