How can we read and write values in a multidimensional array in verilog, i had read in this link regarding different operations that can be done on multidimensional array. like if there is a part of code like this

input [15:0] me;

reg [15:0] p_array [7:0];
reg abc_pqr [2:0];

abc_pqr[0] <= me[0];
abc_pqr[1] <= me[1];
abc_pqr[2] <= me[1];
p_array[abc_pqr[0]] <= me[0];
p_array[abc_pqr[1]] <= me[1];
p_array[abc_pqr[2]] <= me[2];

so is this code will work and will not produce any error?

What is the difference between these two while assigning value

"<=" and "=", i had seen "<=" in most of the places during passing values.


1 Answer 1


This is not one question but breaking down the main points:

<= is a non-blocking assignment used when implying a flip-flop output.
= is a blocking assignment used when implementing combinatorial output.

example usage:

input [10:0] in_data;

reg [11:0] flip_flop;
reg [11:0] next_data

always @(posedge clock) begin
  flip_flop <= next_data;

always @* begin
  next_data = in_data + 11'd1;

You defined 3 different data types:

input [15:0] me;
reg [15:0] p_array [7:0];
reg abc_pqr [2:0];          //Same as reg [0:0] abc_pqr [2:0]

me is a standard 16 bit word. p_array is an 8 deep memory of 16 bit words.
NB: it is typical to define as reg [15:0] p_array [0:7]; abc_pqr [2:0]; is a 3 deep 1bit memory.

You have :

abc_pqr[0] <= me[0]; //This is a 1 bit assignment:
abc_pqr[1] <= me[1];
abc_pqr[2] <= me[2]; //<-- corrected this to 2

Looks valid.

Then :

p_array[abc_pqr[0]] <= me[0];

p_array needs a [7:0] wide index, you have only supplied 1 bit. and a p_array element is 16 bits wide your left hand side is again only 1 bit.

  • \$\begingroup\$ Ok... but what if I declared the array correctly as an array of 16 bit regs and I want to access the low two bits of the 0th entry. Would it be p_array[0][1:0] <= 2'b11; ? I can't get that to work. \$\endgroup\$
    – doug65536
    Jun 19, 2014 at 20:22
  • \$\begingroup\$ @doug65536 if you would like to write a question with what you are trying to do and what you have tried then we can have a go at answering it, link back to here if you want to provide more context. NB i think Stackoverflow is the better place for Verilog programming questions. \$\endgroup\$ Jun 19, 2014 at 21:37

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