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132 lines
4.7 KiB
Verilog
132 lines
4.7 KiB
Verilog
/*
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###########################################################################
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# Function: A mailbox FIFO with a FIFO empty/full flags that can be used as
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# interrupts. Status of the FIFO can be polled.
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#
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# E_MAILBOXLO = lower 32 bits of FIFO entry
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# E_MAILBOXHI = upper 32 bits of FIFO entry
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#
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# Notes: System takes care of not overflowing the FIFO
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# Reading the E_MAILBOXHI causes rd pointer to update to next entry
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# E_MAILBOXLO/E_MAILBOXHI must be consecutive addresses for write.
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# The "embox_not_empty" will stay high as long as there are messages
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#
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# How to use: 1.) Connect "embox_not_empty" to interrupt input line
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# 2.) Write an ISR to respond to interrupt line that:
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# -reads E_MAILBOXLO, then
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# -reads E_MAILBOXHI, then
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# -finishes ISR
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###########################################################################
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*/
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module emailbox (/*AUTOARG*/
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// Outputs
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mi_dout, mailbox_full, mailbox_not_empty,
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// Inputs
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reset, wr_clk, rd_clk, mi_en, mi_we, mi_addr, mi_din
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);
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parameter DW = 32; //data width of fifo
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parameter AW = 32; //data width of fifo
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parameter PW = 104; //packet size
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parameter RFAW = 5; //address bus width
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parameter GROUP = 4'h0; //address map group
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parameter ID = 12'h800; //link id
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/*****************************/
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/*RESET */
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/*****************************/
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input reset; //asynchronous reset
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input wr_clk; //write clock
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input rd_clk; //read clock
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/*****************************/
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/*READ INTERFACE */
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/*****************************/
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input mi_en;
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input mi_we;
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input [19:0] mi_addr;
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input [63:0] mi_din; //assumes write interface is 64 bits
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output [31:0] mi_dout;
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/*****************************/
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/*MAILBOX OUTPUTS */
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/*****************************/
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output mailbox_full;
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output mailbox_not_empty;
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/*****************************/
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/*REGISTERS */
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/*****************************/
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reg [DW-1:0] mi_dout;
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/*****************************/
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/*WIRES */
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/*****************************/
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wire mailbox_read;
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wire mailbox_pop_fifo;
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wire [2*DW-1:0] mailbox_fifo_data;
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wire mailbox_empty;
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wire mailbox_write;
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/*****************************/
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/*WRITE PORT */
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/*****************************/
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assign mailbox_write = mi_en & mi_we & (mi_addr[RFAW+1:2]==`E_MAILBOXLO);
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/*****************************/
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/*READ BACK DATA */
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/*****************************/
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assign mailbox_pop_fifo = mi_en &
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~mi_we &
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mailbox_not_empty &
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mailbox_read & (mi_addr[RFAW+1:2]==`E_MAILBOXHI); //fifo read
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always @ (posedge rd_clk)
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if(mailbox_read)
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case(mi_addr[RFAW+1:2])
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`E_MAILBOXLO: mi_dout[DW-1:0] <= mailbox_fifo_data[DW-1:0];
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`E_MAILBOXHI: mi_dout[DW-1:0] <= mailbox_fifo_data[2*DW-1:DW];
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default: mi_dout[DW-1:0] <= 32'd0;
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endcase // case (mi_addr[RFAW-1:2])
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/*****************************/
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/*FIFO (64-BIT) */
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/*****************************/
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assign mailbox_not_empty = ~mailbox_empty;
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//BUG! This fifo is currently hard coded to 32 entries
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//Should be parametrized to up to 4096 entries
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fifo_async #(.DW(64), .AW(5)) fifo(// Outputs
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.dout (mailbox_fifo_data[2*DW-1:0]),
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.empty (mailbox_empty),
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.full (mailbox_full),
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.prog_full (),
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//Read Port
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.rd_en (mailbox_pop_fifo),
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.rd_clk (rd_clk),
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//Write Port
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.din (mi_din[63:0]),
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.wr_en (mailbox_write),
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.wr_clk (wr_clk),
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.reset (reset)
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);
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endmodule // emailbox
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/*
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Copyright (C) 2014 Adapteva, Inc.
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Contributed by Andreas Olofsson <andreas@adapteva.com>
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.This program is distributed in the hope
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that it will be useful,but WITHOUT ANY WARRANTY; without even the implied
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warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details. You should have received a copy
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of the GNU General Public License along with this program (see the file
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COPYING). If not, see <http://www.gnu.org/licenses/>.
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*/
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