initial import

tests/openmsp430/rtl/omsp_clock_gate.v

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+//----------------------------------------------------------------------------
+// Copyright (C) 2009 , Olivier Girard
+//
+// 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 authors 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
+//
+//----------------------------------------------------------------------------
+//
+// *File Name: omsp_clock_gate.v
+// 
+// *Module Description:
+//                       Generic clock gate cell for the openMSP430
+//
+// *Author(s):
+//              - Olivier Girard,    olgirard@gmail.com
+//
+//----------------------------------------------------------------------------
+// $Rev: 103 $
+// $LastChangedBy: olivier.girard $
+// $LastChangedDate: 2011-03-05 15:44:48 +0100 (Sat, 05 Mar 2011) $
+//----------------------------------------------------------------------------
+
+module  omsp_clock_gate (
+
+// OUTPUTs
+    gclk,                      // Gated clock
+
+// INPUTs
+    clk,                       // Clock
+    enable,                    // Clock enable
+    scan_enable                // Scan enable (active during scan shifting)
+);
+
+// OUTPUTs
+//=========
+output         gclk;           // Gated clock
+
+// INPUTs
+//=========
+input          clk;            // Clock
+input          enable;         // Clock enable
+input          scan_enable;    // Scan enable (active during scan shifting)
+
+
+//=============================================================================
+// CLOCK GATE: LATCH + AND
+//=============================================================================
+   
+// Enable clock gate during scan shift
+// (the gate itself is checked with the scan capture cycle)
+wire    enable_in =   (enable | scan_enable);
+
+// LATCH the enable signal
+reg     enable_latch;
+always @(clk or enable_in)
+  if (~clk)
+    enable_latch <= enable_in;
+
+// AND gate
+assign  gclk      =  (clk & enable_latch);
+
+
+endmodule // omsp_clock_gate
+
+