How to implement buffer in vhdl

[xilinx1001]

Hi,

I need to implement a circular buffer in VHDL

I have 2 signals which I need to display on seven segment (3 digit number using 3 sevensegment)

I need to display a different characters on 4th seven segment for each signal value

And how can I display them circularly


Thanks
xilinx1001

 

[barry]

What do you mean "display them circularly"? A circular buffer is pretty easy to implement, but I'm not sure what else you need.

type dbuff is array (0 to 7) of std_logic_vector(7 downto 0);	
signal parmbuff:dbuff;
      |
      |
      |
process(clk)
begin 
        if clk='1' and clk'event then
               parmbuff(1 to 7)<=parmbuff(0 to 6); 
               parmbuff(0)<=parmbuff(7);
       end if;
end process;

 

[xilinx1001]

Hi barry,

thanks for your reply.

I need each vector(data) with a special character like a,b,c etc

How can I do this?

Thanks in advance
xilinx1001

 

[barry]

I'm ASSUMING (since you don't explain it) that you want to alternate displaying two 3-digit signals, right? And you want a fourth character to indicate which signal you are displaying, right? If that's the case, then what you really want is a multiplexer(not a circular buffer) and two 4-vector arrays, each consisting of 3 digits and one 'character' . During the first period your display data comes from the the first array, and during the other period data comes from the other array, right?

 

[xilinx1001]

Hi barry,

Exactly, this is my question

I need to display like this

How this can be done?

THANKS
xilinx1001

 

[barry]

I think I just explained it. Here's a little more detail.

1) Set up two arrays that contain the 4 characters to display (3 digits + character)
2) Create four 2-input multiplexers that select the 4 characters to display
3) Create a module that will convert your 4 characters to 7-segment data (if necessary)
3a) Are you multiplexing the data to the display or driving the 4 digits directly? If multiplexing the display, you'll have to deal with that also.
4) Creating the timing signals for driving the mux.

 

[xilinx1001]

Hi barry,

I am using multiplexing for 3 digits(data) to display.

so, I need to create 2 arrays now. one for character and another for 3 digits data.

And I need to write the code in a way that when 1st 3 digit data is selected then character a must display on segment . Right?

 

[barry]

you need 2 arrays of four elements: each array has a character and 3 digits==>

Array 1: Ca D3a D2a D1a
Array 2: Cb D3b D2b D1b

Each of the elements maps to one of the 7-segment displays

 

[xilinx1001]

Hi,

I tried to do like you said.

I defined an array and when I tried to assign the values to it like below:

type dbuff is array (0 to 3) of std_logic_vector(3 downto 0);
signal x:dbuff;
dbuff<=unit1;
dbuff<=tens1;
dbuff<=hundreds1 ;
dbuff<="0000" ;

I am getting some error like this:

Line 53. parse error, unexpected IDENTIFIER

Is this the correct way of assigning values to array


Thanks
xilinx1001

 

[barry]

1) I don't know where line 53 is
2) You should be assigning the values to "x", not "dbuff". dbuff is a TYPE, x is the signal.
2) I don't know what "unit1", "tens1" etc. are. They'd better be std_logic_vector(3 downto 0).
3) I assume your assignments occur after the "begin" keyword, NOT as you've shown them.