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-rw-r--r--common/rtl/novena_clkmgr.v77
-rw-r--r--common/rtl/novena_dcm_spartan6.v173
2 files changed, 210 insertions, 40 deletions
diff --git a/common/rtl/novena_clkmgr.v b/common/rtl/novena_clkmgr.v
index 97db451..38a89eb 100644
--- a/common/rtl/novena_clkmgr.v
+++ b/common/rtl/novena_clkmgr.v
@@ -42,47 +42,40 @@ module novena_clkmgr
input wire gclk_p, // signal from clock pins
input wire gclk_n, //
- input wire reset_mcu_b, // cpu reset (async)
+ input wire reset_mcu_b, // cpu reset (async, active-low)
output wire sys_clk, // buffered system clock output
- output wire sys_rst // system reset output (sync)
+ output wire sys_rst_n // system reset output (async set, sync clear, active-low)
);
- //
- // Ports
- //
-
-
- //
- // IBUFGDS
- //
- (* BUFFER_TYPE="NONE" *)
- wire gclk;
-
- IBUFGDS IBUFGDS_gclk
- (
- .I(gclk_p),
- .IB(gclk_n),
- .O(gclk)
- );
-
//
- // DCM
+ // Wrapper for Xilinx-specific DCM (Digital Clock Managar) primitive.
//
- wire dcm_reset; // dcm reset
- wire dcm_locked; // output clock valid
- wire gclk_missing; // no input clock
-
- clkmgr_dcm dcm
- (
- .CLK_IN1(gclk),
- .RESET(dcm_reset),
- .INPUT_CLK_STOPPED(gclk_missing),
-
- .CLK_OUT1(sys_clk),
- .CLK_VALID(dcm_locked)
- );
+
+ wire gclk; // buffered input clock
+ wire dcm_reset; // dcm reset
+ wire dcm_locked; // output clock valid
+ wire gclk_missing; // missing input clock
+
+ novena_dcm_spartan6 #
+ (
+ .CLK_OUT_MUL (2), // 2..32
+ .CLK_OUT_DIV (2) // 1..32
+ )
+ dcm_s6
+ (
+ .clk_in_p(gclk_p),
+ .clk_in_n(gclk_n),
+
+ .reset_in(dcm_reset),
+
+ .gclk_out(gclk),
+ .gclk_missing_out(gclk_missing),
+
+ .clk_out(sys_clk),
+ .clk_valid_out (dcm_locked)
+ );
//
@@ -90,7 +83,8 @@ module novena_clkmgr
//
/* DCM should be reset on power-up, when input clock is stopped or when the
- * CPU gets reset.
+ * CPU gets reset. Note that DCM requires active-high reset, so the shift
+ * register is preloaded with 1's and gradually filled with 0's.
*/
reg [15: 0] dcm_rst_shreg = {16{1'b1}}; // 16-bit shift register
@@ -109,18 +103,21 @@ module novena_clkmgr
// System Reset Logic
//
- /* System reset is asserted for 16 cycles whenever DCM aquires lock. */
+ /* System reset is asserted for 16 cycles whenever DCM aquires lock. Note that system
+ * reset is active-low, so the shift register is preloaded with 0's and gradually filled
+ * with 1's afterwards.
+ */
- reg [15: 0] sys_rst_shreg = {16{1'b1}}; // 16-bit shift register
+ reg [15: 0] sys_rst_shreg = {16{1'b0}}; // 16-bit shift register
always @(posedge sys_clk or negedge reset_mcu_b or posedge gclk_missing or negedge dcm_locked)
//
if ((reset_mcu_b == 1'b0) || (gclk_missing == 1'b1) || (dcm_locked == 1'b0))
- sys_rst_shreg <= {16{1'b1}};
+ sys_rst_shreg <= {16{1'b0}};
else if (dcm_locked == 1'b1)
- sys_rst_shreg <= {sys_rst_shreg[14:0], 1'b0};
+ sys_rst_shreg <= {sys_rst_shreg[14:0], 1'b1};
- assign sys_rst = sys_rst_shreg[15];
+ assign sys_rst_n = sys_rst_shreg[15];
endmodule
diff --git a/common/rtl/novena_dcm_spartan6.v b/common/rtl/novena_dcm_spartan6.v
new file mode 100644
index 0000000..ab60254
--- /dev/null
+++ b/common/rtl/novena_dcm_spartan6.v
@@ -0,0 +1,173 @@
+//======================================================================
+//
+// novena_dcm_spartan6.v
+// ---------------------
+// Wrapper file for Xilinx-specific DCM_SP primitive and supporting
+// vendor-specific stuff. This wrapper can be used to get rid of
+// "Clocking Wizard" IP core and associated coregen pain.
+//
+//
+// 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.
+//
+//======================================================================
+
+`timescale 1ns / 1ps
+
+module novena_dcm_spartan6
+ (
+ input wire clk_in_p,
+ input wire clk_in_n,
+
+ input wire reset_in,
+
+ output wire gclk_out,
+ output wire gclk_missing_out,
+
+ output wire clk_out,
+ output wire clk_valid_out
+ );
+
+
+ //
+ // Parameters
+ //
+ parameter CLK_OUT_MUL = 2; // multiply factor for output clock frequency (2..32)
+ parameter CLK_OUT_DIV = 2; // divide factor for output clock frequency (1..32)
+
+ //
+ // IBUFGDS
+ //
+
+ /* Xilinx-specific primitive to handle LVDS input signal. */
+
+ (* BUFFER_TYPE="NONE" *)
+ wire clk_in;
+
+ IBUFGDS IBUFGDS_gclk
+ (
+ .I(clk_in_p),
+ .IB(clk_in_n),
+ .O(clk_in)
+ );
+
+
+ //
+ // DCM_SP
+ //
+
+ /* Xilinx-specific primitive. */
+
+ wire dcm_clk_0; // primary (1:1) output
+ wire dcm_clk_feedback; // PLL feedback path
+ wire dcm_clk_fx; // synthesized frequency
+ wire dcm_locked_int; // locked flag
+ wire [ 7: 0] dcm_status_int; // status of DCM
+
+ DCM_SP #
+ (
+ .STARTUP_WAIT ("FALSE"),
+ .DESKEW_ADJUST ("SYSTEM_SYNCHRONOUS"),
+ .CLK_FEEDBACK ("1X"),
+
+ .PHASE_SHIFT (0),
+ .CLKOUT_PHASE_SHIFT ("NONE"),
+
+ .CLKIN_PERIOD (20.0), // 50 MHz => 20 ns
+ .CLKIN_DIVIDE_BY_2 ("FALSE"),
+
+ .CLKDV_DIVIDE (5.000),
+ .CLKFX_MULTIPLY (CLK_OUT_MUL),
+ .CLKFX_DIVIDE (CLK_OUT_DIV)
+ )
+ DCM_SP_inst
+ (
+ .RST (reset_in),
+
+ .CLKIN (gclk_out),
+ .CLKFB (dcm_clk_feedback),
+ .CLKDV (),
+
+ .CLK0 (dcm_clk_0),
+ .CLK90 (),
+ .CLK180 (),
+ .CLK270 (),
+
+ .CLK2X (),
+ .CLK2X180 (),
+
+ .CLKFX (dcm_clk_fx),
+ .CLKFX180 (),
+
+ .PSCLK (1'b0),
+ .PSEN (1'b0),
+ .PSINCDEC (1'b0),
+ .PSDONE (),
+
+ .LOCKED (dcm_locked_int),
+ .STATUS (dcm_status_int),
+
+ .DSSEN (1'b0)
+ );
+
+
+ //
+ // Mapping
+ //
+ assign gclk_out = clk_in;
+ assign gclk_missing_out = dcm_status_int[1];
+ assign clk_valid_out = dcm_locked_int & ((dcm_status_int[2:1] == 2'b00) ? 1'b1 : 1'b0);
+
+
+ //
+ // Feedback Path
+ //
+
+ /* DCM_SP requires BUFG primitive in its feedback path. */
+
+ BUFG BUFG_feedback
+ (
+ .I (dcm_clk_0),
+ .O (dcm_clk_feedback)
+ );
+
+ //
+ // Output Buffer
+ //
+
+ /* Connect system clock to global clocking network. */
+
+ BUFG BUFG_output
+ (
+ .I (dcm_clk_fx),
+ .O (clk_out)
+ );
+
+
+endmodule