array of array

M

Marco

Guest
Hi,
I need to create something like a matrix, say 32 bits on each row and
up to 4 rows.
That's why on my Spartan3 I have to receive 32 bits word from a serial
port and I have to store them (I know I can just place a 32x4 bits long
vector and store the data in the same row, but I'd like to learn more
about array of array).
I wrote:

type row is array (cmd_buffer_word downto 0) of std_logic;
type cmd_buffer is array (cmd_buffer_depth downto 0) of row;

now, how could I transfer the whole 32 bits data inside a vector called
cmd_tmp_buffer into the second row of my cmd_buffer?

This following line is wrong, but it may help you understand what I'm
trying to do:
cmd_buffer(1, 31 downto 0) <= cmd_tmp_buffer(31 downto 0);

Thanks,
Marco
 
"Marco" <marco@marylon.com> wrote in message
news:1148456364.753997.228730@j55g2000cwa.googlegroups.com...
Hi,
I need to create something like a matrix, say 32 bits on each row and
up to 4 rows.
I wrote:

type row is array (cmd_buffer_word downto 0) of std_logic;
type cmd_buffer is array (cmd_buffer_depth downto 0) of row;

now, how could I transfer the whole 32 bits data inside a vector called
cmd_tmp_buffer into the second row of my cmd_buffer?

This following line is wrong, but it may help you understand what I'm
trying to do:
cmd_buffer(1, 31 downto 0) <= cmd_tmp_buffer(31 downto 0);
Click to expand...
You are confusing an "array of arrays" with a multi-dimensional array. You
may also be confusing a type with a signal.

First you need to declare a signal of type cmd_buffer:

signal my_cmd_buffer : cmd_buffer;

Given this definition, you should write:

my_cmd_buffer(1)(31 downto 0) <= cmd_tmp_buffer(31 downto 0);

Or, if the constant cmd_buffer_word is in fact 31, you can write simply:

my_cmd_buffer(1) <= cmd_tmp_buffer; -- much nicer!

Usually an array of arrays works out easier (in terms of syntax) than the
equivalent 2-D array. However, sometimes only a 2-D array type will do (for
example, if both dimensions have to be of arbitrary size at the point of
definition).

HTH,

-Ben-
 
Hi Ben
thanks for your help, but I get on XST 7.1:
"Type of my_cmd_buffer is incompatible with type of cmd_tmp_buffer."
Your explanation made more clear the use of array and type, I'll make
some more test to undrstand why I get the error.
Thanks, Marco
 
I used 2 different ways, each one getting the same error:

1) signal cmd_tmp_buffer : std_logic_vector(31 downto 0);

2) type cmd_buffer_type is array (31 downto 0) of std_logic;
signal cmd_tmp_buffer : cmd_buffer_type;

Marco
 
"Marco" <marco@marylon.com> wrote in message
news:1148460020.931904.87190@j33g2000cwa.googlegroups.com...
Hi Ben
thanks for your help, but I get on XST 7.1:
"Type of my_cmd_buffer is incompatible with type of cmd_tmp_buffer."
Click to expand...
This is probably because of VHDL's strong typing. What type is
cmd_tmp_buffer?

If it is a std_logic_vector, then it is not of the same type as the rows of
my_cmd_buffer (which are of type row).

You should probably change your definition of type "row" to this:

subtype row is std_logic_vector(cmd_buffer_word downto 0);

Then your types will be compatible again.

Cheers,

-Ben-
 
"Marco" <marco@marylon.com> wrote in message
news:1148460427.715860.306030@u72g2000cwu.googlegroups.com...
I used 2 different ways, each one getting the same error:

1) signal cmd_tmp_buffer : std_logic_vector(31 downto 0);

2) type cmd_buffer_type is array (31 downto 0) of std_logic;
signal cmd_tmp_buffer : cmd_buffer_type;
Click to expand...
This is very confusing without being able to see all the code! :)

I just managed to compile the following succesfully, FWIW:

subtype my_word_t is std_logic_vector(31 downto 0);
type my_word_array_t is array(0 to 3) of my_word_t;

signal my_word1, my_word2 : my_word_t;
signal my_array : my_word_array_t;

my_array(1) <= my_word1;
my_word2 <= my_array(2);


Cheers,

-Ben-
 
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