Hardware Design: SIE
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| 1 | // ============================================================================= |
| 2 | // COPYRIGHT NOTICE |
| 3 | // Copyright 2006 (c) Lattice Semiconductor Corporation |
| 4 | // ALL RIGHTS RESERVED |
| 5 | // This confidential and proprietary software may be used only as authorised by |
| 6 | // a licensing agreement from Lattice Semiconductor Corporation. |
| 7 | // The entire notice above must be reproduced on all authorized copies and |
| 8 | // copies may only be made to the extent permitted by a licensing agreement from |
| 9 | // Lattice Semiconductor Corporation. |
| 10 | // |
| 11 | // Lattice Semiconductor Corporation TEL : 1-800-Lattice (USA and Canada) |
| 12 | // 5555 NE Moore Court 408-826-6000 (other locations) |
| 13 | // Hillsboro, OR 97124 web : http://www.latticesemi.com/ |
| 14 | // U.S.A email: techsupport@latticesemi.com |
| 15 | // =============================================================================/ |
| 16 | // FILE DETAILS |
| 17 | // Project : LatticeMico32 |
| 18 | // File : lm32_shifter.v |
| 19 | // Title : Barrel shifter |
| 20 | // Dependencies : lm32_include.v |
| 21 | // Version : 6.1.17 |
| 22 | // ============================================================================= |
| 23 | |
| 24 | `include "lm32_include.v" |
| 25 | |
| 26 | ///////////////////////////////////////////////////// |
| 27 | // Module interface |
| 28 | ///////////////////////////////////////////////////// |
| 29 | |
| 30 | module lm32_shifter ( |
| 31 | // ----- Inputs ------- |
| 32 | clk_i, |
| 33 | rst_i, |
| 34 | stall_x, |
| 35 | direction_x, |
| 36 | sign_extend_x, |
| 37 | operand_0_x, |
| 38 | operand_1_x, |
| 39 | // ----- Outputs ------- |
| 40 | shifter_result_m |
| 41 | ); |
| 42 | |
| 43 | ///////////////////////////////////////////////////// |
| 44 | // Inputs |
| 45 | ///////////////////////////////////////////////////// |
| 46 | |
| 47 | input clk_i; // Clock |
| 48 | input rst_i; // Reset |
| 49 | input stall_x; // Stall instruction in X stage |
| 50 | input direction_x; // Direction to shift |
| 51 | input sign_extend_x; // Whether shift is arithmetic (1'b1) or logical (1'b0) |
| 52 | input [`LM32_WORD_RNG] operand_0_x; // Operand to shift |
| 53 | input [`LM32_WORD_RNG] operand_1_x; // Operand that specifies how many bits to shift by |
| 54 | |
| 55 | ///////////////////////////////////////////////////// |
| 56 | // Outputs |
| 57 | ///////////////////////////////////////////////////// |
| 58 | |
| 59 | output [`LM32_WORD_RNG] shifter_result_m; // Result of shift |
| 60 | wire [`LM32_WORD_RNG] shifter_result_m; |
| 61 | |
| 62 | ///////////////////////////////////////////////////// |
| 63 | // Internal nets and registers |
| 64 | ///////////////////////////////////////////////////// |
| 65 | |
| 66 | reg direction_m; |
| 67 | reg [`LM32_WORD_RNG] left_shift_result; |
| 68 | reg [`LM32_WORD_RNG] right_shift_result; |
| 69 | reg [`LM32_WORD_RNG] left_shift_operand; |
| 70 | wire [`LM32_WORD_RNG] right_shift_operand; |
| 71 | wire fill_value; |
| 72 | wire [`LM32_WORD_RNG] right_shift_in; |
| 73 | |
| 74 | integer shift_idx_0; |
| 75 | integer shift_idx_1; |
| 76 | |
| 77 | ///////////////////////////////////////////////////// |
| 78 | // Combinational Logic |
| 79 | ///////////////////////////////////////////////////// |
| 80 | |
| 81 | // Select operands - To perform a left shift, we reverse the bits and perform a right shift |
| 82 | always @* |
| 83 | begin |
| 84 | for (shift_idx_0 = 0; shift_idx_0 < `LM32_WORD_WIDTH; shift_idx_0 = shift_idx_0 + 1) |
| 85 | left_shift_operand[`LM32_WORD_WIDTH-1-shift_idx_0] = operand_0_x[shift_idx_0]; |
| 86 | end |
| 87 | assign right_shift_operand = direction_x == `LM32_SHIFT_OP_LEFT ? left_shift_operand : operand_0_x; |
| 88 | |
| 89 | // Determine fill value for right shift - Sign bit for arithmetic shift, or zero for logical shift |
| 90 | assign fill_value = (sign_extend_x == `TRUE) && (direction_x == `LM32_SHIFT_OP_RIGHT) |
| 91 | ? operand_0_x[`LM32_WORD_WIDTH-1] |
| 92 | : 1'b0; |
| 93 | |
| 94 | // Determine bits to shift in for right shift or rotate |
| 95 | assign right_shift_in = {`LM32_WORD_WIDTH{fill_value}}; |
| 96 | |
| 97 | // Reverse bits to get left shift result |
| 98 | always @* |
| 99 | begin |
| 100 | for (shift_idx_1 = 0; shift_idx_1 < `LM32_WORD_WIDTH; shift_idx_1 = shift_idx_1 + 1) |
| 101 | left_shift_result[`LM32_WORD_WIDTH-1-shift_idx_1] = right_shift_result[shift_idx_1]; |
| 102 | end |
| 103 | |
| 104 | // Select result |
| 105 | assign shifter_result_m = direction_m == `LM32_SHIFT_OP_LEFT ? left_shift_result : right_shift_result; |
| 106 | |
| 107 | ///////////////////////////////////////////////////// |
| 108 | // Sequential Logic |
| 109 | ///////////////////////////////////////////////////// |
| 110 | |
| 111 | // Perform right shift |
| 112 | always @(posedge clk_i `CFG_RESET_SENSITIVITY) |
| 113 | begin |
| 114 | if (rst_i == `TRUE) |
| 115 | begin |
| 116 | right_shift_result <= {`LM32_WORD_WIDTH{1'b0}}; |
| 117 | direction_m <= `FALSE; |
| 118 | end |
| 119 | else |
| 120 | begin |
| 121 | if (stall_x == `FALSE) |
| 122 | begin |
| 123 | right_shift_result <= {right_shift_in, right_shift_operand} >> operand_1_x[`LM32_SHIFT_RNG]; |
| 124 | direction_m <= direction_x; |
| 125 | end |
| 126 | end |
| 127 | end |
| 128 | |
| 129 | endmodule |
| 130 |
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