Sat, 06 Aug 2011 00:02:46 +0100
[UPSTREAM PULL] Update baseline to LatticeMico32 v3.8 from Diamond 1.3-lm32 distribution package (datestamp May 2011)
| philpem@26 | 1 | // ================================================================== |
| philpem@26 | 2 | // >>>>>>>>>>>>>>>>>>>>>>> COPYRIGHT NOTICE <<<<<<<<<<<<<<<<<<<<<<<<< |
| philpem@26 | 3 | // ------------------------------------------------------------------ |
| philpem@26 | 4 | // Copyright (c) 2006-2011 by Lattice Semiconductor Corporation |
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| philpem@26 | 9 | // |
| philpem@26 | 10 | // Permission: |
| philpem@26 | 11 | // |
| philpem@26 | 12 | // Lattice Semiconductor grants permission to use this code |
| philpem@26 | 13 | // pursuant to the terms of the Lattice Semiconductor Corporation |
| philpem@26 | 14 | // Open Source License Agreement. |
| philpem@26 | 15 | // |
| philpem@26 | 16 | // Disclaimer: |
| philpem@0 | 17 | // |
| philpem@26 | 18 | // Lattice Semiconductor provides no warranty regarding the use or |
| philpem@26 | 19 | // functionality of this code. It is the user's responsibility to |
| philpem@26 | 20 | // verify the user’s design for consistency and functionality through |
| philpem@26 | 21 | // the use of formal verification methods. |
| philpem@26 | 22 | // |
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| philpem@26 | 35 | // |
| philpem@26 | 36 | // -------------------------------------------------------------------- |
| philpem@0 | 37 | // FILE DETAILS |
| philpem@0 | 38 | // Project : LatticeMico32 |
| philpem@0 | 39 | // File : lm32_adder.v |
| philpem@0 | 40 | // Title : Integer adder / subtractor with comparison flag generation |
| philpem@0 | 41 | // Dependencies : lm32_include.v |
| philpem@0 | 42 | // Version : 6.1.17 |
| philpem@0 | 43 | // : Initial Release |
| philpem@0 | 44 | // Version : 7.0SP2, 3.0 |
| philpem@0 | 45 | // : No Change |
| philpem@0 | 46 | // Version : 3.1 |
| philpem@0 | 47 | // : No Change |
| philpem@0 | 48 | // ============================================================================= |
| philpem@0 | 49 | |
| philpem@0 | 50 | `include "lm32_include.v" |
| philpem@0 | 51 | |
| philpem@0 | 52 | ///////////////////////////////////////////////////// |
| philpem@0 | 53 | // Module interface |
| philpem@0 | 54 | ///////////////////////////////////////////////////// |
| philpem@0 | 55 | |
| philpem@0 | 56 | module lm32_adder ( |
| philpem@0 | 57 | // ----- Inputs ------- |
| philpem@0 | 58 | adder_op_x, |
| philpem@0 | 59 | adder_op_x_n, |
| philpem@0 | 60 | operand_0_x, |
| philpem@0 | 61 | operand_1_x, |
| philpem@0 | 62 | // ----- Outputs ------- |
| philpem@0 | 63 | adder_result_x, |
| philpem@0 | 64 | adder_carry_n_x, |
| philpem@0 | 65 | adder_overflow_x |
| philpem@0 | 66 | ); |
| philpem@0 | 67 | |
| philpem@0 | 68 | ///////////////////////////////////////////////////// |
| philpem@0 | 69 | // Inputs |
| philpem@0 | 70 | ///////////////////////////////////////////////////// |
| philpem@0 | 71 | |
| philpem@0 | 72 | input adder_op_x; // Operating to perform, 0 for addition, 1 for subtraction |
| philpem@0 | 73 | input adder_op_x_n; // Inverted version of adder_op_x |
| philpem@0 | 74 | input [`LM32_WORD_RNG] operand_0_x; // Operand to add, or subtract from |
| philpem@0 | 75 | input [`LM32_WORD_RNG] operand_1_x; // Opearnd to add, or subtract by |
| philpem@0 | 76 | |
| philpem@0 | 77 | ///////////////////////////////////////////////////// |
| philpem@0 | 78 | // Outputs |
| philpem@0 | 79 | ///////////////////////////////////////////////////// |
| philpem@0 | 80 | |
| philpem@0 | 81 | output [`LM32_WORD_RNG] adder_result_x; // Result of addition or subtraction |
| philpem@0 | 82 | wire [`LM32_WORD_RNG] adder_result_x; |
| philpem@0 | 83 | output adder_carry_n_x; // Inverted carry |
| philpem@0 | 84 | wire adder_carry_n_x; |
| philpem@0 | 85 | output adder_overflow_x; // Indicates if overflow occured, only valid for subtractions |
| philpem@0 | 86 | reg adder_overflow_x; |
| philpem@0 | 87 | |
| philpem@0 | 88 | ///////////////////////////////////////////////////// |
| philpem@0 | 89 | // Internal nets and registers |
| philpem@0 | 90 | ///////////////////////////////////////////////////// |
| philpem@0 | 91 | |
| philpem@0 | 92 | wire a_sign; // Sign (i.e. positive or negative) of operand 0 |
| philpem@0 | 93 | wire b_sign; // Sign of operand 1 |
| philpem@0 | 94 | wire result_sign; // Sign of result |
| philpem@0 | 95 | |
| philpem@0 | 96 | ///////////////////////////////////////////////////// |
| philpem@0 | 97 | // Instantiations |
| philpem@0 | 98 | ///////////////////////////////////////////////////// |
| philpem@0 | 99 | |
| philpem@0 | 100 | lm32_addsub addsub ( |
| philpem@0 | 101 | // ----- Inputs ----- |
| philpem@0 | 102 | .DataA (operand_0_x), |
| philpem@0 | 103 | .DataB (operand_1_x), |
| philpem@0 | 104 | .Cin (adder_op_x), |
| philpem@0 | 105 | .Add_Sub (adder_op_x_n), |
| philpem@0 | 106 | // ----- Ouputs ----- |
| philpem@0 | 107 | .Result (adder_result_x), |
| philpem@0 | 108 | .Cout (adder_carry_n_x) |
| philpem@0 | 109 | ); |
| philpem@0 | 110 | |
| philpem@0 | 111 | ///////////////////////////////////////////////////// |
| philpem@0 | 112 | // Combinational Logic |
| philpem@0 | 113 | ///////////////////////////////////////////////////// |
| philpem@0 | 114 | |
| philpem@0 | 115 | // Extract signs of operands and result |
| philpem@0 | 116 | |
| philpem@0 | 117 | assign a_sign = operand_0_x[`LM32_WORD_WIDTH-1]; |
| philpem@0 | 118 | assign b_sign = operand_1_x[`LM32_WORD_WIDTH-1]; |
| philpem@0 | 119 | assign result_sign = adder_result_x[`LM32_WORD_WIDTH-1]; |
| philpem@0 | 120 | |
| philpem@0 | 121 | // Determine whether an overflow occured when performing a subtraction |
| philpem@0 | 122 | |
| philpem@0 | 123 | always @(*) |
| philpem@0 | 124 | begin |
| philpem@0 | 125 | // +ve - -ve = -ve -> overflow |
| philpem@0 | 126 | // -ve - +ve = +ve -> overflow |
| philpem@0 | 127 | if ( (!a_sign & b_sign & result_sign) |
| philpem@0 | 128 | || (a_sign & !b_sign & !result_sign) |
| philpem@0 | 129 | ) |
| philpem@0 | 130 | adder_overflow_x = `TRUE; |
| philpem@0 | 131 | else |
| philpem@0 | 132 | adder_overflow_x = `FALSE; |
| philpem@0 | 133 | end |
| philpem@0 | 134 | |
| philpem@0 | 135 | endmodule |
| philpem@0 | 136 |