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verilog-axi/rtl/axi_ram.v
Alex Forencich 83b5d30347 Rewrite resets
2021-02-17 18:06:47 -08:00

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/*
Copyright (c) 2018 Alex Forencich
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
// Language: Verilog 2001
`timescale 1ns / 1ps
/*
* AXI4 RAM
*/
module axi_ram #
(
// Width of data bus in bits
parameter DATA_WIDTH = 32,
// Width of address bus in bits
parameter ADDR_WIDTH = 16,
// Width of wstrb (width of data bus in words)
parameter STRB_WIDTH = (DATA_WIDTH/8),
// Width of ID signal
parameter ID_WIDTH = 8,
// Extra pipeline register on output
parameter PIPELINE_OUTPUT = 0
)
(
input wire clk,
input wire rst,
input wire [ID_WIDTH-1:0] s_axi_awid,
input wire [ADDR_WIDTH-1:0] s_axi_awaddr,
input wire [7:0] s_axi_awlen,
input wire [2:0] s_axi_awsize,
input wire [1:0] s_axi_awburst,
input wire s_axi_awlock,
input wire [3:0] s_axi_awcache,
input wire [2:0] s_axi_awprot,
input wire s_axi_awvalid,
output wire s_axi_awready,
input wire [DATA_WIDTH-1:0] s_axi_wdata,
input wire [STRB_WIDTH-1:0] s_axi_wstrb,
input wire s_axi_wlast,
input wire s_axi_wvalid,
output wire s_axi_wready,
output wire [ID_WIDTH-1:0] s_axi_bid,
output wire [1:0] s_axi_bresp,
output wire s_axi_bvalid,
input wire s_axi_bready,
input wire [ID_WIDTH-1:0] s_axi_arid,
input wire [ADDR_WIDTH-1:0] s_axi_araddr,
input wire [7:0] s_axi_arlen,
input wire [2:0] s_axi_arsize,
input wire [1:0] s_axi_arburst,
input wire s_axi_arlock,
input wire [3:0] s_axi_arcache,
input wire [2:0] s_axi_arprot,
input wire s_axi_arvalid,
output wire s_axi_arready,
output wire [ID_WIDTH-1:0] s_axi_rid,
output wire [DATA_WIDTH-1:0] s_axi_rdata,
output wire [1:0] s_axi_rresp,
output wire s_axi_rlast,
output wire s_axi_rvalid,
input wire s_axi_rready
);
parameter VALID_ADDR_WIDTH = ADDR_WIDTH - $clog2(STRB_WIDTH);
parameter WORD_WIDTH = STRB_WIDTH;
parameter WORD_SIZE = DATA_WIDTH/WORD_WIDTH;
// bus width assertions
initial begin
if (WORD_SIZE * STRB_WIDTH != DATA_WIDTH) begin
$error("Error: AXI data width not evenly divisble (instance %m)");
$finish;
end
if (2**$clog2(WORD_WIDTH) != WORD_WIDTH) begin
$error("Error: AXI word width must be even power of two (instance %m)");
$finish;
end
end
localparam [0:0]
READ_STATE_IDLE = 1'd0,
READ_STATE_BURST = 1'd1;
reg [0:0] read_state_reg = READ_STATE_IDLE, read_state_next;
localparam [1:0]
WRITE_STATE_IDLE = 2'd0,
WRITE_STATE_BURST = 2'd1,
WRITE_STATE_RESP = 2'd2;
reg [1:0] write_state_reg = WRITE_STATE_IDLE, write_state_next;
reg mem_wr_en;
reg mem_rd_en;
reg [ID_WIDTH-1:0] read_id_reg = {ID_WIDTH{1'b0}}, read_id_next;
reg [ADDR_WIDTH-1:0] read_addr_reg = {ADDR_WIDTH{1'b0}}, read_addr_next;
reg [7:0] read_count_reg = 8'd0, read_count_next;
reg [2:0] read_size_reg = 3'd0, read_size_next;
reg [1:0] read_burst_reg = 2'd0, read_burst_next;
reg [ID_WIDTH-1:0] write_id_reg = {ID_WIDTH{1'b0}}, write_id_next;
reg [ADDR_WIDTH-1:0] write_addr_reg = {ADDR_WIDTH{1'b0}}, write_addr_next;
reg [7:0] write_count_reg = 8'd0, write_count_next;
reg [2:0] write_size_reg = 3'd0, write_size_next;
reg [1:0] write_burst_reg = 2'd0, write_burst_next;
reg s_axi_awready_reg = 1'b0, s_axi_awready_next;
reg s_axi_wready_reg = 1'b0, s_axi_wready_next;
reg [ID_WIDTH-1:0] s_axi_bid_reg = {ID_WIDTH{1'b0}}, s_axi_bid_next;
reg s_axi_bvalid_reg = 1'b0, s_axi_bvalid_next;
reg s_axi_arready_reg = 1'b0, s_axi_arready_next;
reg [ID_WIDTH-1:0] s_axi_rid_reg = {ID_WIDTH{1'b0}}, s_axi_rid_next;
reg [DATA_WIDTH-1:0] s_axi_rdata_reg = {DATA_WIDTH{1'b0}}, s_axi_rdata_next;
reg s_axi_rlast_reg = 1'b0, s_axi_rlast_next;
reg s_axi_rvalid_reg = 1'b0, s_axi_rvalid_next;
reg [ID_WIDTH-1:0] s_axi_rid_pipe_reg = {ID_WIDTH{1'b0}};
reg [DATA_WIDTH-1:0] s_axi_rdata_pipe_reg = {DATA_WIDTH{1'b0}};
reg s_axi_rlast_pipe_reg = 1'b0;
reg s_axi_rvalid_pipe_reg = 1'b0;
// (* RAM_STYLE="BLOCK" *)
reg [DATA_WIDTH-1:0] mem[(2**VALID_ADDR_WIDTH)-1:0];
wire [VALID_ADDR_WIDTH-1:0] s_axi_awaddr_valid = s_axi_awaddr >> (ADDR_WIDTH - VALID_ADDR_WIDTH);
wire [VALID_ADDR_WIDTH-1:0] s_axi_araddr_valid = s_axi_araddr >> (ADDR_WIDTH - VALID_ADDR_WIDTH);
wire [VALID_ADDR_WIDTH-1:0] read_addr_valid = read_addr_reg >> (ADDR_WIDTH - VALID_ADDR_WIDTH);
wire [VALID_ADDR_WIDTH-1:0] write_addr_valid = write_addr_reg >> (ADDR_WIDTH - VALID_ADDR_WIDTH);
assign s_axi_awready = s_axi_awready_reg;
assign s_axi_wready = s_axi_wready_reg;
assign s_axi_bid = s_axi_bid_reg;
assign s_axi_bresp = 2'b00;
assign s_axi_bvalid = s_axi_bvalid_reg;
assign s_axi_arready = s_axi_arready_reg;
assign s_axi_rid = PIPELINE_OUTPUT ? s_axi_rid_pipe_reg : s_axi_rid_reg;
assign s_axi_rdata = PIPELINE_OUTPUT ? s_axi_rdata_pipe_reg : s_axi_rdata_reg;
assign s_axi_rresp = 2'b00;
assign s_axi_rlast = PIPELINE_OUTPUT ? s_axi_rlast_pipe_reg : s_axi_rlast_reg;
assign s_axi_rvalid = PIPELINE_OUTPUT ? s_axi_rvalid_pipe_reg : s_axi_rvalid_reg;
integer i, j;
initial begin
// two nested loops for smaller number of iterations per loop
// workaround for synthesizer complaints about large loop counts
for (i = 0; i < 2**VALID_ADDR_WIDTH; i = i + 2**(VALID_ADDR_WIDTH/2)) begin
for (j = i; j < i + 2**(VALID_ADDR_WIDTH/2); j = j + 1) begin
mem[j] = 0;
end
end
end
always @* begin
write_state_next = WRITE_STATE_IDLE;
mem_wr_en = 1'b0;
write_id_next = write_id_reg;
write_addr_next = write_addr_reg;
write_count_next = write_count_reg;
write_size_next = write_size_reg;
write_burst_next = write_burst_reg;
s_axi_awready_next = 1'b0;
s_axi_wready_next = 1'b0;
s_axi_bid_next = s_axi_bid_reg;
s_axi_bvalid_next = s_axi_bvalid_reg && !s_axi_bready;
case (write_state_reg)
WRITE_STATE_IDLE: begin
s_axi_awready_next = 1'b1;
if (s_axi_awready && s_axi_awvalid) begin
write_id_next = s_axi_awid;
write_addr_next = s_axi_awaddr;
write_count_next = s_axi_awlen;
write_size_next = s_axi_awsize < $clog2(STRB_WIDTH) ? s_axi_awsize : $clog2(STRB_WIDTH);
write_burst_next = s_axi_awburst;
s_axi_awready_next = 1'b0;
s_axi_wready_next = 1'b1;
write_state_next = WRITE_STATE_BURST;
end else begin
write_state_next = WRITE_STATE_IDLE;
end
end
WRITE_STATE_BURST: begin
s_axi_wready_next = 1'b1;
if (s_axi_wready && s_axi_wvalid) begin
mem_wr_en = 1'b1;
if (write_burst_reg != 2'b00) begin
write_addr_next = write_addr_reg + (1 << write_size_reg);
end
write_count_next = write_count_reg - 1;
if (write_count_reg > 0) begin
write_state_next = WRITE_STATE_BURST;
end else begin
s_axi_wready_next = 1'b0;
if (s_axi_bready || !s_axi_bvalid) begin
s_axi_bid_next = write_id_reg;
s_axi_bvalid_next = 1'b1;
s_axi_awready_next = 1'b1;
write_state_next = WRITE_STATE_IDLE;
end else begin
write_state_next = WRITE_STATE_RESP;
end
end
end else begin
write_state_next = WRITE_STATE_BURST;
end
end
WRITE_STATE_RESP: begin
if (s_axi_bready || !s_axi_bvalid) begin
s_axi_bid_next = write_id_reg;
s_axi_bvalid_next = 1'b1;
s_axi_awready_next = 1'b1;
write_state_next = WRITE_STATE_IDLE;
end else begin
write_state_next = WRITE_STATE_RESP;
end
end
endcase
end
always @(posedge clk) begin
write_state_reg <= write_state_next;
write_id_reg <= write_id_next;
write_addr_reg <= write_addr_next;
write_count_reg <= write_count_next;
write_size_reg <= write_size_next;
write_burst_reg <= write_burst_next;
s_axi_awready_reg <= s_axi_awready_next;
s_axi_wready_reg <= s_axi_wready_next;
s_axi_bid_reg <= s_axi_bid_next;
s_axi_bvalid_reg <= s_axi_bvalid_next;
for (i = 0; i < WORD_WIDTH; i = i + 1) begin
if (mem_wr_en & s_axi_wstrb[i]) begin
mem[write_addr_valid][WORD_SIZE*i +: WORD_SIZE] <= s_axi_wdata[WORD_SIZE*i +: WORD_SIZE];
end
end
if (rst) begin
write_state_reg <= WRITE_STATE_IDLE;
s_axi_awready_reg <= 1'b0;
s_axi_wready_reg <= 1'b0;
s_axi_bvalid_reg <= 1'b0;
end
end
always @* begin
read_state_next = READ_STATE_IDLE;
mem_rd_en = 1'b0;
s_axi_rid_next = s_axi_rid_reg;
s_axi_rlast_next = s_axi_rlast_reg;
s_axi_rvalid_next = s_axi_rvalid_reg && !(s_axi_rready || (PIPELINE_OUTPUT && !s_axi_rvalid_pipe_reg));
read_id_next = read_id_reg;
read_addr_next = read_addr_reg;
read_count_next = read_count_reg;
read_size_next = read_size_reg;
read_burst_next = read_burst_reg;
s_axi_arready_next = 1'b0;
case (read_state_reg)
READ_STATE_IDLE: begin
s_axi_arready_next = 1'b1;
if (s_axi_arready && s_axi_arvalid) begin
read_id_next = s_axi_arid;
read_addr_next = s_axi_araddr;
read_count_next = s_axi_arlen;
read_size_next = s_axi_arsize < $clog2(STRB_WIDTH) ? s_axi_arsize : $clog2(STRB_WIDTH);
read_burst_next = s_axi_arburst;
s_axi_arready_next = 1'b0;
read_state_next = READ_STATE_BURST;
end else begin
read_state_next = READ_STATE_IDLE;
end
end
READ_STATE_BURST: begin
if (s_axi_rready || (PIPELINE_OUTPUT && !s_axi_rvalid_pipe_reg) || !s_axi_rvalid_reg) begin
mem_rd_en = 1'b1;
s_axi_rvalid_next = 1'b1;
s_axi_rid_next = read_id_reg;
s_axi_rlast_next = read_count_reg == 0;
if (read_burst_reg != 2'b00) begin
read_addr_next = read_addr_reg + (1 << read_size_reg);
end
read_count_next = read_count_reg - 1;
if (read_count_reg > 0) begin
read_state_next = READ_STATE_BURST;
end else begin
s_axi_arready_next = 1'b1;
read_state_next = READ_STATE_IDLE;
end
end else begin
read_state_next = READ_STATE_BURST;
end
end
endcase
end
always @(posedge clk) begin
read_state_reg <= read_state_next;
read_id_reg <= read_id_next;
read_addr_reg <= read_addr_next;
read_count_reg <= read_count_next;
read_size_reg <= read_size_next;
read_burst_reg <= read_burst_next;
s_axi_arready_reg <= s_axi_arready_next;
s_axi_rid_reg <= s_axi_rid_next;
s_axi_rlast_reg <= s_axi_rlast_next;
s_axi_rvalid_reg <= s_axi_rvalid_next;
if (mem_rd_en) begin
s_axi_rdata_reg <= mem[read_addr_valid];
end
if (!s_axi_rvalid_pipe_reg || s_axi_rready) begin
s_axi_rid_pipe_reg <= s_axi_rid_reg;
s_axi_rdata_pipe_reg <= s_axi_rdata_reg;
s_axi_rlast_pipe_reg <= s_axi_rlast_reg;
s_axi_rvalid_pipe_reg <= s_axi_rvalid_reg;
end
if (rst) begin
read_state_reg <= READ_STATE_IDLE;
s_axi_arready_reg <= 1'b0;
s_axi_rvalid_reg <= 1'b0;
s_axi_rvalid_pipe_reg <= 1'b0;
end
end
endmodule
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