micheleandClaude Sonnet 5
7e2711fa27
Bumps ADDR_WIDTH's default from 22 to 23 bits across every RTL module (neuron_memory, layer_sequencer, spi_engine, spi_neuron_top, mem_arbiter, int8_memory_access, memory_interface, psram_controller, memory_model) and every testbench that mirrors it, so the system's byte-address space reaches the full 8 MiB the recommended PSRAM part (ISSI IS66WVE4M16EBLL-70BLI, docs/FPGA-Neural-Hardware-Design.md §3) actually provides -- previously only 4 MiB (half the chip) was reachable, since int8_memory_access.v's byte->word address shift (addr >> 1) turned the old 22-bit byte address into only 21 real word bits, one short of the chip's real 22-bit word address (A0-A21). At 23 bits, that same shift lands exactly on all 22 chip address lines, so the whole part is usable now instead of deferred to a future widening. Also fixes a stray 22'd11-sized literal in layer_sequencer.v's descriptor-table address increment (numerically already safe via Verilog's zero-extension, but now correctly unsized so it always matches ADDR_WIDTH instead of silently assuming 22). Updated docs/FPGA-NeuralNetwork-Engine.md's SPI protocol address-field note (23 bits, top 1 reserved bit instead of 2) and docs/FPGA-Neural-Hardware-Design.md's PSRAM section (the "chip has one spare address line" framing is gone now that all 22 are wired and used). Full regression (all 11 ADDR_WIDTH-touching testbenches, plus a Yosys elaboration check of spi_neuron_top with the new default and no override) passes clean. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01WQV3vS9TXaGDJ5cRfnfidt
179 lines
5.1 KiB
Verilog
179 lines
5.1 KiB
Verilog
module int8_memory_access #(
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parameter ADDR_WIDTH = 23
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)(
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input wire clk,
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input wire rst,
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// ============================================================
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// INT8 interface
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//
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// addr is BYTE address
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// ============================================================
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input wire req,
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input wire wr,
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input wire [ADDR_WIDTH-1:0] addr,
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input wire signed [7:0] wdata,
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output reg signed [7:0] rdata,
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output reg ready,
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// ============================================================
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// 16-bit memory interface
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// ============================================================
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output reg mem_req,
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output reg mem_wr,
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output reg [ADDR_WIDTH-1:0] mem_addr,
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output reg [15:0] mem_wdata,
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output reg mem_lb_n,
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output reg mem_ub_n,
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input wire [15:0] mem_rdata,
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input wire mem_ready
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);
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// ============================================================
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// State machine
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// ============================================================
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localparam STATE_IDLE = 2'd0;
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localparam STATE_WAIT = 2'd1;
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reg [1:0] state;
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// ============================================================
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// Latched byte address
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// ============================================================
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reg [ADDR_WIDTH-1:0] addr_reg;
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// ============================================================
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// Main state machine
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// ============================================================
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always @(posedge clk) begin
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if (rst) begin
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state <= STATE_IDLE;
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addr_reg <= {ADDR_WIDTH{1'b0}};
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rdata <= 8'sd0;
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ready <= 1'b0;
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mem_req <= 1'b0;
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mem_wr <= 1'b0;
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mem_addr <= {ADDR_WIDTH{1'b0}};
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mem_wdata <= 16'h0000;
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// Active-low byte enables:
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// 1 = disabled
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mem_lb_n <= 1'b1;
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mem_ub_n <= 1'b1;
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end else begin
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// ready is a one-cycle pulse
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ready <= 1'b0;
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// mem_req is a one-cycle pulse
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mem_req <= 1'b0;
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case (state)
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// =================================================
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// IDLE
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// =================================================
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STATE_IDLE: begin
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if (req) begin
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addr_reg <= addr;
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mem_req <= 1'b1;
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mem_wr <= wr;
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// ------------------------------------------------
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// Byte address -> 16-bit word address
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//
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// addr[0] = 0 -> low byte
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// addr[0] = 1 -> high byte
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// ------------------------------------------------
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mem_addr <= addr >> 1;
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// ------------------------------------------------
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// Select byte
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// ------------------------------------------------
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if (addr[0] == 1'b0) begin
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// Low byte
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mem_lb_n <= 1'b0;
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mem_ub_n <= 1'b1;
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// Data goes into DQ[7:0]
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mem_wdata <= {8'h00, wdata};
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end else begin
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// High byte
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mem_lb_n <= 1'b1;
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mem_ub_n <= 1'b0;
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// Data goes into DQ[15:8]
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mem_wdata <= {wdata, 8'h00};
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end
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state <= STATE_WAIT;
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end
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end
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// =================================================
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// WAIT
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// =================================================
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STATE_WAIT: begin
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if (mem_ready) begin
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// ------------------------------------------------
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// Extract requested byte
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// ------------------------------------------------
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if (addr_reg[0] == 1'b0)
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rdata <= mem_rdata[7:0];
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else
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rdata <= mem_rdata[15:8];
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ready <= 1'b1;
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state <= STATE_IDLE;
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end
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end
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// =================================================
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// Default
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// =================================================
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default: begin
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state <= STATE_IDLE;
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mem_req <= 1'b0;
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mem_lb_n <= 1'b1;
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mem_ub_n <= 1'b1;
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end
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endcase
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end
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end
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endmodule |