Verilog multi dimensional array

[harpv]

Which is the right way of declaring a multi dimensional array reg [1:0] variable [N-1:0] or reg [1:0] variable [0:N-1] ? What difference does it make whether you declare it one way or the other?

 

[dave_59]

If you only access the unpacked dimension (the range to the right of the variable) one element at a time, the only difference it makes is if you use $readmem to load the memory from a file, the left range index gets loaded first.

There can be more of a difference in SystemVerilog because it deals with streams of bits that span more than a single element.

 

[harpv]

Thanks for the reply Dave.

The variable I'm talking about is inside a memory model used for simulations. If I use [N-1:0] form instead of the other in my model will it give erroneous results during simulation? I'm not loading the mem using $re

 

[dave_59]

The difference between [N-1:0] and [0:N-1] should not make any difference if you only access one indexed element of a dimension at a time. That is true for any dimension. Are you seeing something that make you think otherwise?

 

[Mina Magdy]

i have faced the same problem before but when i declare both as a packed array but in unpacked array error may due to trying to equaling or comparing the two arrays or display the hole array not one element a time.

 

[dave_59]

With the exception of $readmem, Verilog does not allow you to access more than one unpacked array element at a time. SystemVerilog allows you to copy and compare whole unpacked arrays having the same shape. It also has the "%p" format for displaying aggregate data like unpacked arrays.

 

[Muthuraja.M]

the right way of declaring a multi dimensional array is reg [1:0] variable [0:N-1]. This is the general structure.. It means that the two bits array of N elements have been declared starts from 0 to N...

 

[dave_59]

There is no right way here. It is just what conventions people are used to.

 

[Muthuraja.M]

yes dave_59 most probably the memory array used as reg [1:0] variable [0:N-1]. so only i stated like that.. But actually as your words There is no right way here....