Memory initialization with $readmemh in Verilog - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the $readmemh system task in Verilog?

$readmemh is used to initialize memory arrays in Verilog by reading hexadecimal values from an external file into a memory block.

beginner

How does $readmemh differ from $readmemb?

$readmemh reads memory initialization data in hexadecimal format, while $readmemb reads data in binary format.

beginner

Show a simple example of using $readmemh to initialize a memory array.

reg [7:0] memory [0:15];
initial begin
  $readmemh("memory_init.hex", memory);
end

This loads the contents of memory_init.hex into the memory array at simulation start.

beginner

What format should the file used with $readmemh have?

The file should contain hexadecimal values, one per line or separated by spaces, representing the memory contents to load.

beginner

When is the best time to call $readmemh in your Verilog code?

It is best to call $readmemh inside an initial block so the memory is loaded at the start of simulation.

What does $readmemh do in Verilog?

A Loads memory contents from a hexadecimal file

B Reads binary input from a user

C Writes data to a file

D Initializes registers with zeros

$readmemh loads memory contents from a file with hexadecimal values.

Which file format is used with $readmemh?

A Decimal

B Binary

C Hexadecimal

D ASCII text

$readmemh expects a file with hexadecimal values.

Where should $readmemh be placed in your Verilog code?

A Inside an <code>always</code> block

B Inside an <code>initial</code> block

C Outside any block

D Inside a function

It should be inside an initial block to run once at simulation start.

What is the difference between $readmemh and $readmemb?

A <code>$readmemh</code> reads hex, <code>$readmemb</code> reads binary

B <code>$readmemh</code> writes memory, <code>$readmemb</code> reads memory

C They are the same

D <code>$readmemh</code> reads decimal, <code>$readmemb</code> reads hex

$readmemh reads hexadecimal files; $readmemb reads binary files.

If your memory file has values like 0A 1F 2B, which system task should you use?

A $writememh

B $readmemb

C $display

D $readmemh

Values like 0A are hexadecimal, so use $readmemh.

Explain how to initialize a memory array in Verilog using $readmemh.

Think about when and how the file is read into memory.

Describe the difference between $readmemh and $readmemb and when to use each.

Focus on the file content format.