// SPDX-FileCopyrightText: 2020 Efabless Corporation // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. // SPDX-License-Identifier: Apache-2.0 `default_nettype none //----------------------------------------------------------- // SPI controller for Caravel //----------------------------------------------------------- // housekeeping_spi.v //------------------------------------------------------ // General purpose SPI module for the Caravel chip //------------------------------------------------------ // Written by Tim Edwards // efabless, inc., September 28, 2020 //------------------------------------------------ // This file is distributed free and open source //------------------------------------------------ // SCK --- Clock input // SDI --- Data input // SDO --- Data output // CSB --- Chip select (sense negative) // idata --- Data from chip to transmit out, in 8 bits // odata --- Input data to chip, in 8 bits // addr --- Decoded address to upstream circuits // rdstb --- Read strobe, tells upstream circuit that data will be latched. // wrstb --- Write strobe, tells upstream circuit to latch odata. // Data format (general purpose): // 8 bit format // 1st byte: Command word (see below) // 2nd byte: Address word (register 0 to 255) // 3rd byte: Data word (value 0 to 255) // Command format: // 00000000 No operation // 10000000 Write until CSB raised // 01000000 Read until CSB raised // 11000000 Simultaneous read/write until CSB raised // 11000100 Pass-through read/write to management area flash SPI until CSB raised // 11000010 Pass-through read/write to user area flash SPI until CSB raised // wrnnn000 Read/write as above, for nnn = 1 to 7 bytes, then terminate // Lower three bits are reserved for future use. // All serial bytes are read and written msb first. // Fixed control and status registers // Address 0 is reserved and contains flags for SPI mode. This is // currently undefined and is always value 0. // Address 1 is reserved and contains manufacturer ID low 8 bits. // Address 2 is reserved and contains manufacturer ID high 4 bits. // Address 3 is reserved and contains product ID (8 bits). // Addresses 4 to 7 are reserved and contain the mask ID (32 bits). // Addresses 8 to 255 are available for general purpose use. `define COMMAND 3'b000 `define ADDRESS 3'b001 `define DATA 3'b010 `define USERPASS 3'b100 `define MGMTPASS 3'b101 module housekeeping_spi(reset, SCK, SDI, CSB, SDO, sdoenb, idata, odata, oaddr, rdstb, wrstb, pass_thru_mgmt, pass_thru_mgmt_delay, pass_thru_user, pass_thru_user_delay, pass_thru_mgmt_reset, pass_thru_user_reset); input reset; input SCK; input SDI; input CSB; output SDO; output sdoenb; input [7:0] idata; output [7:0] odata; output [7:0] oaddr; output rdstb; output wrstb; output pass_thru_mgmt; output pass_thru_mgmt_delay; output pass_thru_user; output pass_thru_user_delay; output pass_thru_mgmt_reset; output pass_thru_user_reset; reg [7:0] addr; reg wrstb; reg rdstb; reg sdoenb; reg [2:0] state; reg [2:0] count; reg writemode; reg readmode; reg [2:0] fixed; wire [7:0] odata; reg [6:0] predata; wire [7:0] oaddr; reg [7:0] ldata; reg pass_thru_mgmt; reg pass_thru_mgmt_delay; reg pre_pass_thru_mgmt; reg pass_thru_user; reg pass_thru_user_delay; reg pre_pass_thru_user; wire csb_reset; assign odata = {predata, SDI}; assign oaddr = (state == `ADDRESS) ? {addr[6:0], SDI} : addr; assign SDO = ldata[7]; assign csb_reset = CSB | reset; assign pass_thru_mgmt_reset = pass_thru_mgmt_delay | pre_pass_thru_mgmt; assign pass_thru_user_reset = pass_thru_user_delay | pre_pass_thru_user; // Readback data is captured on the falling edge of SCK so that // it is guaranteed valid at the next rising edge. always @(negedge SCK or posedge csb_reset) begin if (csb_reset == 1'b1) begin wrstb <= 1'b0; ldata <= 8'b00000000; sdoenb <= 1'b1; end else begin // After CSB low, 1st SCK starts command if (state == `DATA) begin if (readmode == 1'b1) begin sdoenb <= 1'b0; if (count == 3'b000) begin ldata <= idata; end else begin ldata <= {ldata[6:0], 1'b0}; // Shift out end end else begin sdoenb <= 1'b1; end // Apply write strobe on SCK negative edge on the next-to-last // data bit so that it updates data on the rising edge of SCK // on the last data bit. if (count == 3'b111) begin if (writemode == 1'b1) begin wrstb <= 1'b1; end end else begin wrstb <= 1'b0; end end else if (state == `MGMTPASS || state == `USERPASS) begin wrstb <= 1'b0; sdoenb <= 1'b0; end else begin wrstb <= 1'b0; sdoenb <= 1'b1; end // ! state `DATA end // ! csb_reset end // always @ ~SCK always @(posedge SCK or posedge csb_reset) begin if (csb_reset == 1'b1) begin // Default state on reset addr <= 8'h00; rdstb <= 1'b0; predata <= 7'b0000000; state <= `COMMAND; count <= 3'b000; readmode <= 1'b0; writemode <= 1'b0; fixed <= 3'b000; pass_thru_mgmt <= 1'b0; pass_thru_mgmt_delay <= 1'b0; pre_pass_thru_mgmt <= 1'b0; pass_thru_user <= 1'b0; pass_thru_user_delay <= 1'b0; pre_pass_thru_user <= 1'b0; end else begin // After csb_reset low, 1st SCK starts command if (state == `COMMAND) begin rdstb <= 1'b0; count <= count + 1; if (count == 3'b000) begin writemode <= SDI; end else if (count == 3'b001) begin readmode <= SDI; end else if (count < 3'b101) begin fixed <= {fixed[1:0], SDI}; end else if (count == 3'b101) begin pre_pass_thru_mgmt <= SDI; end else if (count == 3'b110) begin pre_pass_thru_user <= SDI; pass_thru_mgmt_delay <= pre_pass_thru_mgmt; end else if (count == 3'b111) begin pass_thru_user_delay <= pre_pass_thru_user; if (pre_pass_thru_mgmt == 1'b1) begin state <= `MGMTPASS; pre_pass_thru_mgmt <= 1'b0; end else if (pre_pass_thru_user == 1'b1) begin state <= `USERPASS; pre_pass_thru_user <= 1'b0; end else begin state <= `ADDRESS; end end end else if (state == `ADDRESS) begin count <= count + 1; addr <= {addr[6:0], SDI}; if (count == 3'b111) begin state <= `DATA; if (readmode == 1'b1) begin rdstb <= 1'b1; end end else begin rdstb <= 1'b0; end end else if (state == `DATA) begin predata <= {predata[6:0], SDI}; count <= count + 1; if (count == 3'b111) begin if (fixed == 3'b001) begin state <= `COMMAND; end else if (fixed != 3'b000) begin fixed <= fixed - 1; addr <= addr + 1; // Auto increment address (fixed) end else begin addr <= addr + 1; // Auto increment address (streaming) end if (readmode == 1'b1) begin rdstb <= 1'b1; end end else begin rdstb <= 1'b0; end end else if (state == `MGMTPASS) begin pass_thru_mgmt <= 1'b1; end else if (state == `USERPASS) begin pass_thru_user <= 1'b1; end // ! state `DATA | `MGMTPASS | `USERPASS end // ! csb_reset end // always @ SCK endmodule // housekeeping_spi `default_nettype wire