CODEWITHSUNDEEP
arraysmemoryverilogdrivers
Glenn R. Fisher
Glenn R. Fisher

Reputation: 535

Connecting Verilog Arrays: Multiple Drivers

I am storing a sequence of values in a memory array. When it comes time to output this sequence to an LED display, I am running into an error with multiple drivers.

Here are code snippets that I'm working with:

reg [3:0] p[0:63]; // pattern sequence
....
led = p[playcnt];  // display current pattern; playcnt loops from 0 to 63

It seems like Verilog is trying to connect each register in the memory array to the led output, which results in a "multiple driver" error. Is there any easy way to connect only a single output from the memory array to the led output, and use the playcnt variable as an address into the memory array?

Thanks for your help! It's much appreciated.

Upvotes: 1

Views: 657

Answers (1)

Vasiliy
Vasiliy

Reputation: 16228

Please provide all the code which is relevant to "led" and show what do you mean by "playcnt loops from 0 to 63".

If you have code similar to this:

always_comb 
  for (int playcnt=0; playcnt<64; playcnt++)
    led = p[playcnt];

then you indeed connected all your registers to a single port.

If I understood your intent correctly, then you should have code similar to this (not tested):

reg  [3:0] p [0:63];
reg  [5:0] playcnt;
wire [3:0] led;

always @ (posedge clk or negedge rst)
  if (!rst)
    playcnt[5:0] <= 6'h0;
  else
    playcnt[5:0] <= playcnt[5:0] + 6'h1;

assign led[3:0] = p[playcnt];

Upvotes: 1

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