My current task is to create a memory driver. The specific issue is that I have a shift register designed to concatenate four 8-bit words into one 32-bit and then send that to the output. The module works when being simulated by itself but it fails to respond when connected to other modules. Here's the code :
The shift register code :
module shiftReg (
data_8,
clk,
valid1,
rstn,
data_32,
valid_fifo,
count,
REGA,
REGB,
REGC,
REGD
);
input wire [7:0] data_8;
input wire valid1;
input wire clk;
input wire rstn;
output reg [31:0] data_32;
output reg valid_fifo;
output reg [3:0] count;
output reg [7:0] REGA;
output reg [7:0] REGB;
output reg [7:0] REGC;
output reg [7:0] REGD;
initial
begin
count <= 4'b0001;
REGA <= 8'b0;
REGB <= 8'b0;
REGC <= 8'b0;
REGD <= 8'b0;
valid_fifo <= 1'b0;
end
always @(posedge valid1)
begin
if(~rstn)
begin
count = 4'b0001;
REGA = 0;
REGB = 0;
REGC = 0;
REGD = 0;
end
else if(valid1 == 1'b1)
begin
case (count)
4'b0001: REGA = data_8;
4'b0010: REGB = data_8;
4'b0100: REGC = data_8;
4'b1000: REGD = data_8;
endcase
valid_fifo = 1'b0;
end
if(count == 4'b1000)
begin
data_32 = {REGD,REGC,REGB,REGA};
valid_fifo = 1'b1;
count = 4'b0001;
end
else
begin
count = count << 1;
end
end
endmodule
The module where I am instantiating it is called altogether. Here is the code :
module altogether (
input wire BUTTON_AT,
input wire CLK_AT,
input wire RSTN_AT,
output wire MEM_FULL_AT,
output wire EMPTY_AT,
inout wire VALID_IN_AT,
inout wire [7:0] DATA_8_AT,
inout wire VALID1_AT,
inout wire [31:0] DATA_32_AT,
inout wire STOP_AT,
inout wire VALID_FIFO_AT,
inout wire [31:0] DATA_AT,
inout wire WR_AT,
inout wire [6:0] ADDR_AT,
output wire [7:0] REG_A_AT,
output wire [7:0] REG_B_AT,
output wire [7:0] REG_C_AT,
output wire [7:0] REG_D_AT,
output wire [3:0] COUNT_AT
);
shiftReg shift_register (
.data_8(DATA_8_AT),
.clk(CLK_AT),
.valid1(VALID_1_AT),
.rstn(RSTN_AT),
.data_32(DATA_32_AT),
.valid_fifo(VALID_FIFO_AT),
.REGA(REG_A_AT),
.REGB(REG_B_AT),
.REGC(REG_C_AT),
.REGD(REG_D_AT),
.count(COUNT_AT)
);
For some reason, the valid == 1'b1 condition is not executed when I put the shift register along with everything else. I have really run out of ideas, hope someone manages to look at it and give me an insight.
Somewhere during synthesis you probably got warning that you're using VALID_1_AT signal, which has no driver. That's because in altogether module declaration you define VALID1_AT signal (notice _ missing in signal name). That's why valid1 in your shift register is not driven at all.
You should change:
.valid1(VALID_1_AT)
into:
.valid1(VALID1_AT)
to make it works.