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//////////////////////////////////////////////////////////////////////////////////
// Copyright Ettus Research LLC
// The ZYNQ FIFO slave readback:
// - implements read state machine for 32-bit addressable AXI slave
// - provides readback for state of per-stream fifo pointers
//////////////////////////////////////////////////////////////////////////////////
module zf_slave_readback
#(
parameter CONFIG_BASE = 32'h40000000
)
(
input clk,
input rst,
//------------------------------------------------------------------
//-- control read signals - slave
//------------------------------------------------------------------
input [31:0] AXI_ARADDR,
input AXI_ARVALID,
output AXI_ARREADY,
output [31:0] AXI_RDATA,
output [1:0] AXI_RRESP,
output AXI_RVALID,
input AXI_RREADY,
//------------------------------------------------------------------
// readback interface
//------------------------------------------------------------------
output reg [31:0] addr,
input [31:0] data,
output strobe,
output [31:0] debug
);
////////////////////////////////////////////////////////////////////////
///////////////////////////// Begin R T L //////////////////////////////
////////////////////////////////////////////////////////////////////////
//------------------------------------------------------------------
// Control read state machine responds to AXI control reads
// Used for reading back the state of the various FIFOs
//------------------------------------------------------------------
localparam STATE_ADDR = 0;
localparam STATE_READ = 1;
localparam STATE_DATA = 2;
reg [3:0] state;
always @(posedge clk) begin
if (rst) begin
state <= STATE_ADDR;
addr <= 0;
end
else case (state)
STATE_ADDR: begin
if (AXI_ARVALID && AXI_ARREADY) begin
state <= STATE_READ;
addr <= (AXI_ARADDR - CONFIG_BASE);
end
end
STATE_READ: begin
state <= STATE_DATA;
end
STATE_DATA: begin
if (AXI_RVALID && AXI_RREADY) begin
state <= STATE_ADDR;
end
end
default: state <= STATE_ADDR;
endcase //state
end
assign strobe = AXI_RVALID && AXI_RREADY;
//readback data
assign AXI_RDATA = data;
//only acking address reads from the wait state
assign AXI_ARREADY = (state == STATE_ADDR);
//when to release outputs from the slave
assign AXI_RVALID = (state == STATE_DATA);
assign AXI_RRESP = 0;
endmodule //zf_slave_readback
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