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Diffstat (limited to 'tests/openmsp430/rtl/omsp_clock_mux.v')
| -rw-r--r-- | tests/openmsp430/rtl/omsp_clock_mux.v | 192 |
1 files changed, 192 insertions, 0 deletions
diff --git a/tests/openmsp430/rtl/omsp_clock_mux.v b/tests/openmsp430/rtl/omsp_clock_mux.v new file mode 100644 index 000000000..5f8406ad0 --- /dev/null +++ b/tests/openmsp430/rtl/omsp_clock_mux.v @@ -0,0 +1,192 @@ +//---------------------------------------------------------------------------- +// 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_mux.v +// +// *Module Description: +// Standard clock mux 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_mux ( + +// OUTPUTs + clk_out, // Clock output + +// INPUTs + clk_in0, // Clock input 0 + clk_in1, // Clock input 1 + reset, // Reset + scan_mode, // Scan mode (clk_in0 is selected in scan mode) + select // Clock selection +); + +// OUTPUTs +//========= +output clk_out; // Clock output + +// INPUTs +//========= +input clk_in0; // Clock input 0 +input clk_in1; // Clock input 1 +input reset; // Reset +input scan_mode; // Scan mode (clk_in0 is selected in scan mode) +input select; // Clock selection + + +//===========================================================================================================================// +// 1) CLOCK MUX // +//===========================================================================================================================// +// // +// The following (glitch free) clock mux is implemented as following: // +// // +// // +// // +// // +// +-----. +--------+ +--------+ // +// select >>----+-------------O| \ | | | | +-----. // +// | | |---| D Q |---| D Q |--+-------| \ // +// | +-------O| / | | | | | | |O-+ // +// | | +-----' | | | | | +--O| / | // +// | | | /\ | | /\ | | | +-----' | // +// | | +--+--+--+ +--+--+--+ | | | // +// | | O | | | | // +// | | | | | | | +-----. // +// clk_in0 >>----------------------------------+------------+-----------+ +--| \ // +// | | | | |----<< clk_out // +// | | +---------------------------------------+ +--| / // +// | | | | +-----' // +// | +---------------------------------------------+ | // +// | | | | // +// | | +-----. +--------+ +--------+ | | // +// | +-O| \ | | | | | +-----. | // +// | | |---| D Q |---| D Q |--+-------| \ | // +// +--------------| / | | | | | |O-+ // +// +-----' | | | | +--O| / // +// | /\ | | /\ | | +-----' // +// +--+--+--+ +--+--+--+ | // +// O | | // +// | | | // +// clk_in1 >>----------------------------------+------------+-----------+ // +// // +// // +//===========================================================================================================================// + +//----------------------------------------------------------------------------- +// Wire declarations +//----------------------------------------------------------------------------- + +wire in0_select; +reg in0_select_s; +reg in0_select_ss; +wire in0_enable; + +wire in1_select; +reg in1_select_s; +reg in1_select_ss; +wire in1_enable; + +wire clk_in0_inv; +wire clk_in1_inv; +wire gated_clk_in0; +wire gated_clk_in1; + + +//----------------------------------------------------------------------------- +// CLK_IN0 Selection +//----------------------------------------------------------------------------- + +assign in0_select = ~select & ~in1_select_ss; + +always @ (posedge clk_in0_inv or posedge reset) + if (reset) in0_select_s <= 1'b1; + else in0_select_s <= in0_select; + +always @ (posedge clk_in0 or posedge reset) + if (reset) in0_select_ss <= 1'b1; + else in0_select_ss <= in0_select_s; + +assign in0_enable = in0_select_ss | scan_mode; + + +//----------------------------------------------------------------------------- +// CLK_IN1 Selection +//----------------------------------------------------------------------------- + +assign in1_select = select & ~in0_select_ss; + +always @ (posedge clk_in1_inv or posedge reset) + if (reset) in1_select_s <= 1'b0; + else in1_select_s <= in1_select; + +always @ (posedge clk_in1 or posedge reset) + if (reset) in1_select_ss <= 1'b0; + else in1_select_ss <= in1_select_s; + +assign in1_enable = in1_select_ss & ~scan_mode; + + +//----------------------------------------------------------------------------- +// Clock MUX +//----------------------------------------------------------------------------- +// +// IMPORTANT NOTE: +// Because the clock network is a critical part of the design, +// the following combinatorial logic should be replaced with +// direct instanciation of standard cells from target library. +// Don't forget the "dont_touch" attribute to make sure +// synthesis won't mess it up. +// + +// Replace with standard cell INVERTER +assign clk_in0_inv = ~clk_in0; +assign clk_in1_inv = ~clk_in1; + + +// Replace with standard cell NAND2 +assign gated_clk_in0 = ~(clk_in0_inv & in0_enable); +assign gated_clk_in1 = ~(clk_in1_inv & in1_enable); + + +// Replace with standard cell AND2 +assign clk_out = (gated_clk_in0 & gated_clk_in1); + + + +endmodule // omsp_clock_gate + + + |