1.1 diff -r 000000000000 -r cd0b58aa6f83 lm32_shifter.v 1.2 --- /dev/null Thu Jan 01 00:00:00 1970 +0000 1.3 +++ b/lm32_shifter.v Sun Apr 04 20:40:03 2010 +0100 1.4 @@ -0,0 +1,134 @@ 1.5 +// ============================================================================= 1.6 +// COPYRIGHT NOTICE 1.7 +// Copyright 2006 (c) Lattice Semiconductor Corporation 1.8 +// ALL RIGHTS RESERVED 1.9 +// This confidential and proprietary software may be used only as authorised by 1.10 +// a licensing agreement from Lattice Semiconductor Corporation. 1.11 +// The entire notice above must be reproduced on all authorized copies and 1.12 +// copies may only be made to the extent permitted by a licensing agreement from 1.13 +// Lattice Semiconductor Corporation. 1.14 +// 1.15 +// Lattice Semiconductor Corporation TEL : 1-800-Lattice (USA and Canada) 1.16 +// 5555 NE Moore Court 408-826-6000 (other locations) 1.17 +// Hillsboro, OR 97124 web : http://www.latticesemi.com/ 1.18 +// U.S.A email: techsupport@latticesemi.com 1.19 +// =============================================================================/ 1.20 +// FILE DETAILS 1.21 +// Project : LatticeMico32 1.22 +// File : lm32_shifter.v 1.23 +// Title : Barrel shifter 1.24 +// Dependencies : lm32_include.v 1.25 +// Version : 6.1.17 1.26 +// : Initial Release 1.27 +// Version : 7.0SP2, 3.0 1.28 +// : No Change 1.29 +// Version : 3.1 1.30 +// : No Change 1.31 +// ============================================================================= 1.32 + 1.33 +`include "lm32_include.v" 1.34 + 1.35 +///////////////////////////////////////////////////// 1.36 +// Module interface 1.37 +///////////////////////////////////////////////////// 1.38 + 1.39 +module lm32_shifter ( 1.40 + // ----- Inputs ------- 1.41 + clk_i, 1.42 + rst_i, 1.43 + stall_x, 1.44 + direction_x, 1.45 + sign_extend_x, 1.46 + operand_0_x, 1.47 + operand_1_x, 1.48 + // ----- Outputs ------- 1.49 + shifter_result_m 1.50 + ); 1.51 + 1.52 +///////////////////////////////////////////////////// 1.53 +// Inputs 1.54 +///////////////////////////////////////////////////// 1.55 + 1.56 +input clk_i; // Clock 1.57 +input rst_i; // Reset 1.58 +input stall_x; // Stall instruction in X stage 1.59 +input direction_x; // Direction to shift 1.60 +input sign_extend_x; // Whether shift is arithmetic (1'b1) or logical (1'b0) 1.61 +input [`LM32_WORD_RNG] operand_0_x; // Operand to shift 1.62 +input [`LM32_WORD_RNG] operand_1_x; // Operand that specifies how many bits to shift by 1.63 + 1.64 +///////////////////////////////////////////////////// 1.65 +// Outputs 1.66 +///////////////////////////////////////////////////// 1.67 + 1.68 +output [`LM32_WORD_RNG] shifter_result_m; // Result of shift 1.69 +wire [`LM32_WORD_RNG] shifter_result_m; 1.70 + 1.71 +///////////////////////////////////////////////////// 1.72 +// Internal nets and registers 1.73 +///////////////////////////////////////////////////// 1.74 + 1.75 +reg direction_m; 1.76 +reg [`LM32_WORD_RNG] left_shift_result; 1.77 +reg [`LM32_WORD_RNG] right_shift_result; 1.78 +reg [`LM32_WORD_RNG] left_shift_operand; 1.79 +wire [`LM32_WORD_RNG] right_shift_operand; 1.80 +wire fill_value; 1.81 +wire [`LM32_WORD_RNG] right_shift_in; 1.82 + 1.83 +integer shift_idx_0; 1.84 +integer shift_idx_1; 1.85 + 1.86 +///////////////////////////////////////////////////// 1.87 +// Combinational Logic 1.88 +///////////////////////////////////////////////////// 1.89 + 1.90 +// Select operands - To perform a left shift, we reverse the bits and perform a right shift 1.91 +always @(*) 1.92 +begin 1.93 + for (shift_idx_0 = 0; shift_idx_0 < `LM32_WORD_WIDTH; shift_idx_0 = shift_idx_0 + 1) 1.94 + left_shift_operand[`LM32_WORD_WIDTH-1-shift_idx_0] = operand_0_x[shift_idx_0]; 1.95 +end 1.96 +assign right_shift_operand = direction_x == `LM32_SHIFT_OP_LEFT ? left_shift_operand : operand_0_x; 1.97 + 1.98 +// Determine fill value for right shift - Sign bit for arithmetic shift, or zero for logical shift 1.99 +assign fill_value = (sign_extend_x == `TRUE) && (direction_x == `LM32_SHIFT_OP_RIGHT) 1.100 + ? operand_0_x[`LM32_WORD_WIDTH-1] 1.101 + : 1'b0; 1.102 + 1.103 +// Determine bits to shift in for right shift or rotate 1.104 +assign right_shift_in = {`LM32_WORD_WIDTH{fill_value}}; 1.105 + 1.106 +// Reverse bits to get left shift result 1.107 +always @(*) 1.108 +begin 1.109 + for (shift_idx_1 = 0; shift_idx_1 < `LM32_WORD_WIDTH; shift_idx_1 = shift_idx_1 + 1) 1.110 + left_shift_result[`LM32_WORD_WIDTH-1-shift_idx_1] = right_shift_result[shift_idx_1]; 1.111 +end 1.112 + 1.113 +// Select result 1.114 +assign shifter_result_m = direction_m == `LM32_SHIFT_OP_LEFT ? left_shift_result : right_shift_result; 1.115 + 1.116 +///////////////////////////////////////////////////// 1.117 +// Sequential Logic 1.118 +///////////////////////////////////////////////////// 1.119 + 1.120 +// Perform right shift 1.121 +always @(posedge clk_i `CFG_RESET_SENSITIVITY) 1.122 +begin 1.123 + if (rst_i == `TRUE) 1.124 + begin 1.125 + right_shift_result <= {`LM32_WORD_WIDTH{1'b0}}; 1.126 + direction_m <= `FALSE; 1.127 + end 1.128 + else 1.129 + begin 1.130 + if (stall_x == `FALSE) 1.131 + begin 1.132 + right_shift_result <= {right_shift_in, right_shift_operand} >> operand_1_x[`LM32_SHIFT_RNG]; 1.133 + direction_m <= direction_x; 1.134 + end 1.135 + end 1.136 +end 1.137 + 1.138 +endmodule