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authorPavel V. Shatov <meisterpaul1@yandex.ru>2015-08-27 00:30:26 +0400
committerPavel V. Shatov <meisterpaul1@yandex.ru>2015-08-27 00:30:26 +0400
commitaf78b5570d2229631b287915c25ae3021e9f6982 (patch)
tree2a707866f55fc0718093f12c1a0c1ee00337487f /src/verilog/stm32_fmc
Initial revision of FMC arbiter for Novena's on-board FPGA.HEADmaster
Diffstat (limited to 'src/verilog/stm32_fmc')
-rw-r--r--src/verilog/stm32_fmc/cdc_bus_pulse.v145
-rw-r--r--src/verilog/stm32_fmc/fmc_arbiter.v295
-rw-r--r--src/verilog/stm32_fmc/fmc_arbiter_cdc.v146
-rw-r--r--src/verilog/stm32_fmc/fmc_d_phy.v77
4 files changed, 663 insertions, 0 deletions
diff --git a/src/verilog/stm32_fmc/cdc_bus_pulse.v b/src/verilog/stm32_fmc/cdc_bus_pulse.v
new file mode 100644
index 0000000..cc2d8db
--- /dev/null
+++ b/src/verilog/stm32_fmc/cdc_bus_pulse.v
@@ -0,0 +1,145 @@
+//======================================================================
+//
+// cdc_bus_pulse.v
+// ---------------
+// Clock Domain Crossing handler for the Cryptech Novena
+// FPGA framework design.
+//
+// This module is based on design suggested on page 27 of the
+// paper 'Clock Domain Crossing (CDC) Design & Verification Techniques
+// Using SystemVerilog' by Clifford E. Cummings (Sunburst Design, Inc.)
+//
+//
+// Author: Pavel Shatov
+// Copyright (c) 2015, NORDUnet A/S All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions
+// are met:
+// - Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//
+// - Redistributions in binary form must reproduce the above copyright
+// notice, this list of conditions and the following disclaimer in the
+// documentation and/or other materials provided with the distribution.
+//
+// - Neither the name of the NORDUnet nor the names of its contributors may
+// be used to endorse or promote products derived from this software
+// without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+// PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
+// TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+//======================================================================
+
+module cdc_bus_pulse
+ #(parameter DATA_WIDTH = 32) // width of data bus
+ (
+ input wire src_clk, // source domain clock
+ input wire [DATA_WIDTH-1:0] src_din, // data from source clock domain
+ input wire src_req, // start transfer pulse from source clock domain
+
+ input wire dst_clk, // destination domain clock
+ output wire [DATA_WIDTH-1:0] dst_dout, // data to destination clock domain
+ output wire dst_pulse // transfer done pulse to destination clock domain
+ );
+
+ //
+ // Source Side Registers
+ //
+ reg src_ff = 1'b0; // transfer request flag
+ reg [DATA_WIDTH-1:0] src_latch = {DATA_WIDTH{1'bX}}; // source data buffer
+
+
+ //
+ // Source Request Handler
+ //
+ always @(posedge src_clk)
+ //
+ if (src_req) begin // transfer request pulse?
+ src_ff <= ~src_ff; // toggle transfer request flag...
+ src_latch <= src_din; // ... and capture data in source buffer
+ end
+
+
+ //
+ // Source -> Destination Flag Sync Logic
+ //
+
+ /* ISE may decide to infer SRL here, so we explicitly instantiate slice registers. */
+
+ wire flag_sync_first; // first FF output
+ wire flag_sync_second; // second FF output
+ wire flag_sync_third; // third FF output
+ wire flag_sync_pulse; // flag toggle detector output
+
+ FDCE ff_sync_first
+ (
+ .C(dst_clk),
+ .D(src_ff), // capture flag from another clock domain
+ .Q(flag_sync_first), // metastability can occur here
+ .CLR(1'b0),
+ .CE(1'b1)
+ );
+ FDCE ff_sync_second
+ (
+ .C(dst_clk),
+ .D(flag_sync_first), // synchronize captured flag to remove metastability
+ .Q(flag_sync_second), // and pass it to another flip-flop
+ .CLR(1'b0),
+ .CE(1'b1)
+ );
+ FDCE ff_sync_third
+ (
+ .C(dst_clk),
+ .D(flag_sync_second), // delay synchronized flag in another flip-flip, because we need
+ .Q(flag_sync_third), // two synchronized flag values (current and delayed) to detect its change
+ .CLR(1'b0),
+ .CE(1'b1)
+ );
+
+ // when delayed flag value differs from its current value, it was changed
+ // by the source side, so there must have been a transfer request
+ assign flag_sync_pulse = flag_sync_second ^ flag_sync_third;
+
+
+ //
+ // Destination Side Registers
+ //
+ reg dst_pulse_reg = 1'b0; // transfer done flag
+ reg [DATA_WIDTH-1:0] dst_latch = {DATA_WIDTH{1'bX}}; // destination data buffer
+
+ assign dst_pulse = dst_pulse_reg;
+ assign dst_dout = dst_latch;
+
+ //
+ // Destination Request Handler
+ //
+ always @(posedge dst_clk) begin
+ //
+ dst_pulse_reg <= flag_sync_pulse; // generate pulse if flag change was detected
+ //
+ if (flag_sync_pulse)
+ dst_latch <= src_latch;
+ /* By the time destination side receives synchronized flag
+ * value, data should be stable, we can safely capture and store
+ * it in the destination buffer.
+ */
+
+ end
+
+
+endmodule
+
+//======================================================================
+// EOF cdc_bus_pulse.v
+//======================================================================
diff --git a/src/verilog/stm32_fmc/fmc_arbiter.v b/src/verilog/stm32_fmc/fmc_arbiter.v
new file mode 100644
index 0000000..b9be05c
--- /dev/null
+++ b/src/verilog/stm32_fmc/fmc_arbiter.v
@@ -0,0 +1,295 @@
+//======================================================================
+//
+// fmc_arbiter.v
+// -------------
+// Port arbiter for the FMC interface for the Cryptech
+// Novena FPGA + STM32 Bridge Board framework.
+//
+//
+// Author: Pavel Shatov
+// Copyright (c) 2015, NORDUnet A/S All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions
+// are met:
+// - Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//
+// - Redistributions in binary form must reproduce the above copyright
+// notice, this list of conditions and the following disclaimer in the
+// documentation and/or other materials provided with the distribution.
+//
+// - Neither the name of the NORDUnet nor the names of its contributors may
+// be used to endorse or promote products derived from this software
+// without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+// PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
+// TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+//======================================================================
+
+module fmc_arbiter
+ (
+ // fmc bus
+ fmc_clk,
+ fmc_a, fmc_d,
+ fmc_ne1, fmc_nl, fmc_nwe, fmc_noe, fmc_nwait,
+
+ // system clock
+ sys_clk,
+
+ // user bus
+ sys_addr,
+ sys_wr_en,
+ sys_data_out,
+ sys_rd_en,
+ sys_data_in
+ );
+
+
+ //
+ // Parameters
+ //
+ parameter NUM_ADDR_BITS = 22;
+
+
+ //
+ // Ports
+ //
+ input wire fmc_clk;
+ input wire [NUM_ADDR_BITS-1:0] fmc_a;
+ inout wire [ 31:0] fmc_d;
+ input wire fmc_ne1;
+ input wire fmc_nl;
+ input wire fmc_nwe;
+ input wire fmc_noe;
+ output wire fmc_nwait;
+
+ input wire sys_clk;
+
+ output wire [NUM_ADDR_BITS-1:0] sys_addr;
+ output wire sys_wr_en;
+ output wire [ 31:0] sys_data_out;
+ output wire sys_rd_en;
+ input wire [ 31:0] sys_data_in;
+
+
+ //
+ // Data Bus PHY
+ //
+
+ /* PHY is needed to control bi-directional data bus. */
+
+ wire [31: 0] d_ro; // value read from pins (receiver output)
+ reg [31: 0] d_di; // value drives onto pins (driver input)
+
+ fmc_d_phy #
+ (
+ .BUS_WIDTH(32)
+ )
+ d_phy
+ (
+ .buf_io(fmc_d), // <-- connect directly to top-level bi-dir port
+ .buf_di(d_di),
+ .buf_ro(d_ro),
+ .buf_t(fmc_noe) // <-- bus direction is controlled by STM32
+ );
+
+
+ //
+ // FSM
+ //
+ localparam FMC_FSM_STATE_INIT = 5'b0_0_000; // arbiter is idle
+
+ localparam FMC_FSM_STATE_WRITE_START = 5'b1_1_000; // got address to write at
+ localparam FMC_FSM_STATE_WRITE_LATENCY_1 = 5'b1_1_001; // dummy state to compensate STM32's latency
+ localparam FMC_FSM_STATE_WRITE_LATENCY_2 = 5'b1_1_010; // dummy state to compensate STM32's latency
+ localparam FMC_FSM_STATE_WRITE_LATENCY_3 = 5'b1_1_011; // dummy state to compensate STM32's latency
+ localparam FMC_FSM_STATE_WRITE_DATABEAT = 5'b1_1_100; // got data to write
+ localparam FMC_FSM_STATE_WRITE_WAIT = 5'b1_1_101; // request to user-side logic sent
+ localparam FMC_FSM_STATE_WRITE_DONE = 5'b1_1_111; // user-side logic acknowledged transaction
+
+ localparam FMC_FSM_STATE_READ_START = 5'b1_0_000; // got address to read from
+ localparam FMC_FSM_STATE_READ_LATENCY_1 = 5'b1_0_001; // dummy state to compensate STM32's latency
+ localparam FMC_FSM_STATE_READ_LATENCY_2 = 5'b1_0_010; // dummy state to compensate STM32's latency
+ localparam FMC_FSM_STATE_READ_LATENCY_3 = 5'b1_0_011; // dummy state to compensate STM32's latency
+ localparam FMC_FSM_STATE_READ_WAIT = 5'b1_0_101; // request to user-side logic sent
+ localparam FMC_FSM_STATE_READ_READY = 5'b1_0_110; // got acknowledge from user logic
+ localparam FMC_FSM_STATE_READ_DATABEAT = 5'b1_0_100; // returned data to master
+ localparam FMC_FSM_STATE_READ_DONE = 5'b1_0_111; // transaction complete
+
+ reg [ 4:0] fmc_fsm_state = FMC_FSM_STATE_INIT; // fsm state
+ reg [NUM_ADDR_BITS-1:0] fmc_addr_latch = {NUM_ADDR_BITS{1'bX}}; // transaction address
+ reg [ 31:0] fmc_data_latch = {32{1'bX}}; // write data latch
+
+ /* These flags are used to wake up from INIT state. */
+ wire fmc_write_start_flag = (fmc_ne1 == 1'b0) && (fmc_nwe == 1'b0) && (fmc_nl == 1'b0);
+ wire fmc_read_start_flag = (fmc_ne1 == 1'b0) && (fmc_nwe == 1'b1) && (fmc_nl == 1'b0);
+
+ /* These are transaction response flag and data from user-side logic. */
+ wire fmc_user_ack;
+ wire [31: 0] fmc_user_data;
+
+ //
+ // FSM Transition Logic
+ //
+ always @(posedge fmc_clk)
+ //
+ case (fmc_fsm_state)
+ //
+ // INIT -> WRITE, INIT -> READ
+ //
+ FMC_FSM_STATE_INIT: begin
+ //
+ if (fmc_write_start_flag) fmc_fsm_state <= FMC_FSM_STATE_WRITE_START;
+ if (fmc_read_start_flag) fmc_fsm_state <= FMC_FSM_STATE_READ_START;
+ //
+ end
+ //
+ // WRITE
+ //
+ FMC_FSM_STATE_WRITE_START: fmc_fsm_state <= FMC_FSM_STATE_WRITE_LATENCY_1;
+ FMC_FSM_STATE_WRITE_LATENCY_1: fmc_fsm_state <= FMC_FSM_STATE_WRITE_LATENCY_2;
+ FMC_FSM_STATE_WRITE_LATENCY_2: fmc_fsm_state <= FMC_FSM_STATE_WRITE_LATENCY_3;
+ FMC_FSM_STATE_WRITE_LATENCY_3: fmc_fsm_state <= FMC_FSM_STATE_WRITE_DATABEAT;
+ FMC_FSM_STATE_WRITE_DATABEAT: fmc_fsm_state <= FMC_FSM_STATE_WRITE_WAIT;
+ FMC_FSM_STATE_WRITE_WAIT: if (fmc_user_ack) fmc_fsm_state <= FMC_FSM_STATE_WRITE_DONE;
+ FMC_FSM_STATE_WRITE_DONE: fmc_fsm_state <= FMC_FSM_STATE_INIT;
+ //
+ // READ
+ //
+ FMC_FSM_STATE_READ_START: fmc_fsm_state <= FMC_FSM_STATE_READ_LATENCY_1;
+ FMC_FSM_STATE_READ_LATENCY_1: fmc_fsm_state <= FMC_FSM_STATE_READ_LATENCY_2;
+ FMC_FSM_STATE_READ_LATENCY_2: fmc_fsm_state <= FMC_FSM_STATE_READ_LATENCY_3;
+ FMC_FSM_STATE_READ_LATENCY_3: fmc_fsm_state <= FMC_FSM_STATE_READ_WAIT;
+ FMC_FSM_STATE_READ_WAIT: if (fmc_user_ack) fmc_fsm_state <= FMC_FSM_STATE_READ_READY;
+ FMC_FSM_STATE_READ_READY: fmc_fsm_state <= FMC_FSM_STATE_READ_DATABEAT;
+ FMC_FSM_STATE_READ_DATABEAT: fmc_fsm_state <= FMC_FSM_STATE_READ_DONE;
+ FMC_FSM_STATE_READ_DONE: fmc_fsm_state <= FMC_FSM_STATE_INIT;
+ //
+ default: fmc_fsm_state <= FMC_FSM_STATE_INIT;
+ //
+ endcase
+
+
+ //
+ // Address Latch
+ //
+ always @(posedge fmc_clk)
+ //
+ if ((fmc_fsm_state == FMC_FSM_STATE_INIT) && (fmc_write_start_flag || fmc_read_start_flag))
+ //
+ fmc_addr_latch <= fmc_a;
+
+
+ //
+ // Additional Write Logic (Data Latch)
+ //
+ always @(posedge fmc_clk)
+ //
+ if (fmc_fsm_state == FMC_FSM_STATE_WRITE_LATENCY_3)
+ //
+ fmc_data_latch <= d_ro;
+
+
+ //
+ // Additional Read Logic (Read Latch)
+ //
+
+ /* Note that this register is updated on the falling edge of FMC_CLK, because
+ * STM32 samples bi-directional data bus on the rising edge.
+ */
+
+ always @(negedge fmc_clk)
+ //
+ if (fmc_fsm_state == FMC_FSM_STATE_READ_DATABEAT)
+ //
+ d_di <= fmc_user_data;
+
+
+
+ //
+ // Wait Logic
+ //
+ reg fmc_wait_reg = 1'b0;
+
+ always @(posedge fmc_clk)
+ //
+ begin
+ //
+ if ( (fmc_fsm_state == FMC_FSM_STATE_WRITE_START) ||
+ (fmc_fsm_state == FMC_FSM_STATE_READ_START) )
+ fmc_wait_reg <= 1'b1; // start waiting for read/write to complete
+ /*
+ if ( (fmc_fsm_state == FMC_FSM_STATE_WRITE_DONE) ||
+ (fmc_fsm_state == FMC_FSM_STATE_READ_READY) )
+ fmc_wait_reg <= 1'b0;
+ */
+ if (fmc_fsm_state == FMC_FSM_STATE_INIT)
+ fmc_wait_reg <= 1'b0; // fsm is idle, no need to wait any more
+ //
+ end
+
+ assign fmc_nwait = ~fmc_wait_reg;
+
+
+ /* These flags are used to generate 1-cycle pulses to trigger CDC
+ * transaction. Note that FSM goes from WRITE_DATABEAT to WRITE_WAIT and from
+ * READ_LATENCY_3 to READ_WAIT unconditionally, so these flags will always be
+ * active for 1 cycle only, which is exactly what we need.
+ */
+
+ wire arbiter_write_req_pulse = (fmc_fsm_state == FMC_FSM_STATE_WRITE_DATABEAT) ? 1'b1 : 1'b0;
+ wire arbiter_read_req_pulse = (fmc_fsm_state == FMC_FSM_STATE_READ_LATENCY_3) ? 1'b1 : 1'b0;
+
+ //
+ // CDC Block
+ //
+
+ /* This block is used to transfer request data from FMC_CLK clock domain to
+ * SYS_CLK clock domain and then transfer acknowledge from SYS_CLK to FMC_CLK
+ * clock domain in return. Af first 1+1+22+32 = 56 bits are transfered,
+ * these are: write flag, read flag, address, write data. During read transaction
+ * some bogus write data is passed, which is not used later anyway.
+ * During read requests 32 bits of data are returned, during write requests
+ * 32 bits of bogus data are returned, that are never used later.
+ */
+
+ fmc_arbiter_cdc #
+ (
+ .NUM_ADDR_BITS(NUM_ADDR_BITS)
+ )
+ fmc_cdc
+ (
+ .fmc_clk(fmc_clk),
+
+ .fmc_req(arbiter_write_req_pulse | arbiter_read_req_pulse),
+ .fmc_ack(fmc_user_ack),
+
+ .fmc_din({arbiter_write_req_pulse, arbiter_read_req_pulse, fmc_addr_latch, fmc_data_latch}),
+ .fmc_dout(fmc_user_data),
+
+ .sys_clk(sys_clk),
+ .sys_addr(sys_addr),
+ .sys_wren(sys_wr_en),
+ .sys_data_out(sys_data_out),
+ .sys_rden(sys_rd_en),
+ .sys_data_in(sys_data_in)
+ );
+
+
+endmodule
+
+
+//======================================================================
+// EOF fmc_arbiter.v
+//======================================================================
diff --git a/src/verilog/stm32_fmc/fmc_arbiter_cdc.v b/src/verilog/stm32_fmc/fmc_arbiter_cdc.v
new file mode 100644
index 0000000..4e1437a
--- /dev/null
+++ b/src/verilog/stm32_fmc/fmc_arbiter_cdc.v
@@ -0,0 +1,146 @@
+//======================================================================
+//
+// fmc_arbiter_cdc.v
+// -----------------
+// The actual clock domain crossing handler of the FMC arbiter
+// for the Cryptech Novena FPGA framework.
+//
+//
+// Author: Pavel Shatov
+// Copyright (c) 2015, NORDUnet A/S All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions
+// are met:
+// - Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//
+// - Redistributions in binary form must reproduce the above copyright
+// notice, this list of conditions and the following disclaimer in the
+// documentation and/or other materials provided with the distribution.
+//
+// - Neither the name of the NORDUnet nor the names of its contributors may
+// be used to endorse or promote products derived from this software
+// without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+// PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
+// TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+//======================================================================
+
+module fmc_arbiter_cdc #
+ (
+ parameter NUM_ADDR_BITS = 22
+ )
+ (
+ input wire fmc_clk, // fmc clock
+ input wire fmc_req, // fmc transaction request
+ output wire fmc_ack, // fmc transaction acknowledge
+ input wire [NUM_ADDR_BITS+32+2-1: 0] fmc_din, // data from cpu to fpga (write access)
+ output wire [31: 0] fmc_dout, // data from fpga to cpu (read access)
+
+ input wire sys_clk, // user internal clock
+ output wire [NUM_ADDR_BITS-1: 0] sys_addr, // user access address
+ output wire sys_wren, // user write flag
+ output wire [31: 0] sys_data_out, // user write data
+ output wire sys_rden, // user read flag
+ input wire [31: 0] sys_data_in // user read data
+ );
+
+
+ //
+ // FMC_CLK -> SYS_CLK Request
+ //
+ wire sys_req; // request pulse in sys_clk clock domain
+ wire [NUM_ADDR_BITS+32+2-1: 0] sys_dout; // transaction data in sys_clk clock domain
+
+ cdc_bus_pulse #
+ (
+ .DATA_WIDTH(NUM_ADDR_BITS+32+2) // {write, read, addr, data}
+ )
+ cdc_fmc_sys
+ (
+ .src_clk(fmc_clk),
+ .src_din(fmc_din),
+ .src_req(fmc_req),
+
+ .dst_clk(sys_clk),
+ .dst_dout(sys_dout),
+ .dst_pulse(sys_req)
+ );
+
+
+ //
+ // Output Registers
+ //
+ reg sys_wren_reg = 1'b0;
+ reg sys_rden_reg = 1'b0;
+ reg [NUM_ADDR_BITS-1: 0] sys_addr_reg = {NUM_ADDR_BITS{1'bX}};
+ reg [31: 0] sys_data_out_reg = {32{1'bX}};
+
+ assign sys_wren = sys_wren_reg;
+ assign sys_rden = sys_rden_reg;
+ assign sys_addr = sys_addr_reg;
+ assign sys_data_out = sys_data_out_reg;
+
+
+ //
+ // System (User) Clock Access Handler
+ //
+ always @(posedge sys_clk)
+ //
+ if (sys_req) // request detected?
+ begin
+ sys_wren_reg <= sys_dout[32+NUM_ADDR_BITS+1]; // set write flag if needed
+ sys_rden_reg <= sys_dout[32+NUM_ADDR_BITS+0]; // set read flag if needed
+ sys_addr_reg <= sys_dout[32+NUM_ADDR_BITS-1:32]; // set operation address
+ sys_data_out_reg <= sys_dout[31: 0]; // set data to write
+ end
+ else // no request active
+ begin
+ sys_wren_reg <= 1'b0; // clear write flag
+ sys_rden_reg <= 1'b0; // clear read flag
+ end
+
+
+ //
+ // System Request 2-cycle delay to compensate registered mux delay in user-side logic
+ //
+ reg [ 1: 0] sys_req_dly = 2'b00;
+
+ always @(posedge sys_clk)
+ sys_req_dly <= {sys_req_dly[0], sys_req};
+
+
+ //
+ // SYS_CLK -> FMC_CLK Acknowledge
+ //
+ cdc_bus_pulse #
+ (
+ .DATA_WIDTH(32)
+ )
+ cdc_sys_fmc
+ (
+ .src_clk(sys_clk),
+ .src_din(sys_data_in),
+ .src_req(sys_req_dly[1]),
+
+ .dst_clk(fmc_clk),
+ .dst_dout(fmc_dout),
+ .dst_pulse(fmc_ack)
+ );
+
+endmodule
+
+//======================================================================
+// EOF fmc_arbiter_cdc.v
+//======================================================================
diff --git a/src/verilog/stm32_fmc/fmc_d_phy.v b/src/verilog/stm32_fmc/fmc_d_phy.v
new file mode 100644
index 0000000..ce643bb
--- /dev/null
+++ b/src/verilog/stm32_fmc/fmc_d_phy.v
@@ -0,0 +1,77 @@
+//======================================================================
+//
+// fmc_d_phy.v
+// ------------
+// IO buffer module for the FMC D port.
+//
+//
+// Author: Pavel Shatov
+// Copyright (c) 2015, NORDUnet A/S All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions
+// are met:
+// - Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//
+// - Redistributions in binary form must reproduce the above copyright
+// notice, this list of conditions and the following disclaimer in the
+// documentation and/or other materials provided with the distribution.
+//
+// - Neither the name of the NORDUnet nor the names of its contributors may
+// be used to endorse or promote products derived from this software
+// without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+// PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
+// TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+//======================================================================
+
+module fmc_d_phy
+ #(parameter BUS_WIDTH = 16)
+ (
+ inout wire [BUS_WIDTH-1:0] buf_io, // connect directly to top-level pins
+ input wire [BUS_WIDTH-1:0] buf_di, // drive input (value driven onto pins)
+ output wire [BUS_WIDTH-1:0] buf_ro, // receiver output (value read from pins)
+ input wire buf_t // tristate control (driver is disabled during tristate)
+ );
+
+ //
+ // IOBUFs
+ //
+ genvar i;
+ generate
+ for (i = 0; i < BUS_WIDTH; i = i+1)
+ begin: fmc_d
+ //
+ IOBUF #
+ (
+ .IOSTANDARD("LVCMOS33"),
+ .DRIVE(8),
+ .SLEW("FAST")
+ )
+ IOBUF_inst
+ (
+ .IO(buf_io[i]),
+ .O(buf_ro[i]),
+ .I(buf_di[i]),
+ .T(buf_t)
+ );
+ //
+ end
+ endgenerate
+
+endmodule
+
+//======================================================================
+// EOF fmc_d_phy.v
+//======================================================================