（光盘）MSP430单片机C语言应用程序设计实例精讲

/* 2.4 kbps MELP Proposed Federal Standard speech coder Fixed-point C code, version 1.0 Copyright (c) 1998, Texas Instruments, Inc. Texas Instruments has intellectual property rights on the MELP algorithm. The Texas Instruments contact for licensing issues for commercial and non-government use is William Gordon, Director, Government Contracts, Texas Instruments Incorporated, Semiconductor Group (phone 972 480 7442). The fixed-point version of the voice codec Mixed Excitation Linear Prediction (MELP) is based on specifications on the C-language software simulation contained in GSM 06.06 which is protected by copyright and is the property of the European Telecommunications Standards Institute (ETSI). This standard is available from the ETSI publication office tel. +33 (0)4 92 94 42 58. ETSI has granted a license to United States Department of Defense to use the C-language software simulation contained in GSM 06.06 for the purposes of the development of a fixed-point version of the voice codec Mixed Excitation Linear Prediction (MELP). Requests for authorization to make other use of the GSM 06.06 or otherwise distribute or modify them need to be addressed to the ETSI Secretariat fax: +33 493 65 47 16. */ /*************************************************************************** * * File Name: mathhalf.c * * Purpose: Contains functions which implement the primitive * arithmetic operations. * * The functions in this file are listed below. Some of them are * defined in terms of other basic operations. One of the * routines, saturate() is static. This is not a basic * operation, and is not reference outside the scope of this * file. * * * abs_s() * add() * divide_s() * extract_h() * extract_l() * L_abs() * L_add() * L_deposit_h() * L_deposit_l() * L_mac() * L_msu() * L_mult() * L_negate() * L_shift_r() * L_shl() * L_shr() * L_sub() * mac_r() * msu_r() * mult() * mult_r() * negate() * norm_l() * norm_s() * round() * saturate() * shift_r() * shl() * shr() * sub() * **************************************************************************/ #include "typedefs.h" #include "mathhalf.h" #include "mathdp31.h" /*************************************************************************** * * FUNCTION NAME: saturate * * PURPOSE: * * Limit the 32 bit input to the range of a 16 bit word. * * * INPUTS: * * L_var1 * 32 bit long signed integer (Longword) whose value * falls in the range * 0x8000 0000 <= L_var1 <= 0x7fff ffff. * * OUTPUTS: * * none * * RETURN VALUE: * * swOut * 16 bit short signed integer (Shortword) whose value * falls in the range * 0xffff 8000 <= swOut <= 0x0000 7fff. * * KEYWORDS: saturation, limiting, limit, saturate, 16 bits * *************************************************************************/ static Shortword saturate(Longword L_var1) { Shortword swOut; if (L_var1 > SW_MAX) { swOut = SW_MAX; } else if (L_var1 < SW_MIN) { swOut = SW_MIN; } else { swOut = (Shortword) L_var1; } return (swOut); } /*************************************************************************** * * FUNCTION NAME: divide_s * * PURPOSE: * * Divide var1 by var2. Note that both must be positive, and * var1 >= var2. The output is set to 0 if invalid input is * provided. * * INPUTS: * * var1 * 16 bit short signed integer (Shortword) whose value * falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff. * var2 * 16 bit short signed integer (Shortword) whose value * falls in the range 0xffff 8000 <= var2 <= 0x0000 7fff. * * OUTPUTS: * * none * * RETURN VALUE: * * swOut * 16 bit short signed integer (Shortword) whose value * falls in the range * 0xffff 8000 <= swOut <= 0x0000 7fff. * * IMPLEMENTATION: * * In the case where var1==var2 the function returns 0x7fff. The output * is undefined for invalid inputs. This implementation returns zero * and issues a warning via stdio if invalid input is presented. * * KEYWORDS: divide * *************************************************************************/ Shortword divide_s(Shortword var1, Shortword var2) { Longword L_div; Shortword swOut; if (var1 < 0 || var2 < 0 || var1 > var2) { /* undefined output for invalid input into divide_s */ return ((Shortword)0); } if (var1 == var2) return ((Shortword)0x7fff); L_div = ((0x00008000L * (Longword) var1) / (Longword) var2); swOut = saturate(L_div); return (swOut); } /*************************************************************************** * * FUNCTION NAME: L_deposit_l * * PURPOSE: * * Put the 16 bit input into the 16 LSB's of the output Longword with * sign extension i.e. the top 16 bits are set to either 0 or 0xffff. * * INPUTS: * * var1 * 16 bit short signed integer (Shortword) whose value * falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff. * * OUTPUTS: * * none * * RETURN VALUE: * * L_Out * 32 bit long signed integer (Longword) whose value * falls in the range * 0xffff 8000 <= L_var1 <= 0x0000 7fff. * * KEYWORDS: deposit, assign * *************************************************************************/ Longword L_deposit_l(Shortword var1) { Longword L_Out; L_Out = var1; return (L_Out); } /*************************************************************************** * * FUNCTION NAME: L_deposit_h * * PURPOSE: * * Put the 16 bit input into the 16 MSB's of the output Longword. The * LS 16 bits are zeroed. * * INPUTS: * * var1 * 16 bit short signed integer (Shortword) whose value * falls in the range 0xffff 8000 <= var1 <= 0x0000 7fff. * * OUTPUTS: * * none * * RETURN VALUE: * * L_Out * 32 bit long signed integer (Longword) whose value * falls in the range * 0x8000 0000 <= L_var1 <= 0x7fff 0000. * * * KEYWORDS: deposit, assign, fractional assign * *************************************************************************/ Longword L_deposit_h(Shortword var1) { Longword L_var2; L_var2 = (Longword) var1 << 16; return (L_var2); } /*************************************************************************** * * FUNCTION NAME: extract_l * * PURPOSE: * * Extract the 16 LS bits of a 32 bit Longword. Return the 16 bit * number as a Shortword. The upper portion of the input Longword * has no impact whatsoever on the output. * * INPUTS: * * L_var1 * 32 bit long signed integer (Longword) whose value * falls in the range * 0x8000 0000 <= L_var1 <= 0x7fff ffff. * * OUTPUTS: * * none * * RETURN VALUE: * * swOut * 16 bit short signed integer (Shortword) whose value * falls in the range * 0xffff 8000 <= swOut <= 0x0000 7fff. * * * KEYWORDS: extract, as