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49 <div class="headertitle">
50 <h1>arm_fir_decimate_q15.c</h1> </div>
52 <div class="contents">
53 <a href="arm__fir__decimate__q15_8c.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment"><a name="l00001"></a>00001 <span class="comment">/* ---------------------------------------------------------------------- </span>
54 <a name="l00002"></a>00002 <span class="comment">* Copyright (C) 2010 ARM Limited. All rights reserved. </span>
55 <a name="l00003"></a>00003 <span class="comment">* </span>
56 <a name="l00004"></a>00004 <span class="comment">* $Date: 15. July 2011 </span>
57 <a name="l00005"></a>00005 <span class="comment">* $Revision: V1.0.10 </span>
58 <a name="l00006"></a>00006 <span class="comment">* </span>
59 <a name="l00007"></a>00007 <span class="comment">* Project: CMSIS DSP Library </span>
60 <a name="l00008"></a>00008 <span class="comment">* Title: arm_fir_decimate_q15.c </span>
61 <a name="l00009"></a>00009 <span class="comment">* </span>
62 <a name="l00010"></a>00010 <span class="comment">* Description: Q15 FIR Decimator. </span>
63 <a name="l00011"></a>00011 <span class="comment">* </span>
64 <a name="l00012"></a>00012 <span class="comment">* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0</span>
65 <a name="l00013"></a>00013 <span class="comment">* </span>
66 <a name="l00014"></a>00014 <span class="comment">* Version 1.0.10 2011/7/15 </span>
67 <a name="l00015"></a>00015 <span class="comment">* Big Endian support added and Merged M0 and M3/M4 Source code. </span>
68 <a name="l00016"></a>00016 <span class="comment">* </span>
69 <a name="l00017"></a>00017 <span class="comment">* Version 1.0.3 2010/11/29 </span>
70 <a name="l00018"></a>00018 <span class="comment">* Re-organized the CMSIS folders and updated documentation. </span>
71 <a name="l00019"></a>00019 <span class="comment">* </span>
72 <a name="l00020"></a>00020 <span class="comment">* Version 1.0.2 2010/11/11 </span>
73 <a name="l00021"></a>00021 <span class="comment">* Documentation updated. </span>
74 <a name="l00022"></a>00022 <span class="comment">* </span>
75 <a name="l00023"></a>00023 <span class="comment">* Version 1.0.1 2010/10/05 </span>
76 <a name="l00024"></a>00024 <span class="comment">* Production release and review comments incorporated. </span>
77 <a name="l00025"></a>00025 <span class="comment">* </span>
78 <a name="l00026"></a>00026 <span class="comment">* Version 1.0.0 2010/09/20 </span>
79 <a name="l00027"></a>00027 <span class="comment">* Production release and review comments incorporated </span>
80 <a name="l00028"></a>00028 <span class="comment">* </span>
81 <a name="l00029"></a>00029 <span class="comment">* Version 0.0.7 2010/06/10 </span>
82 <a name="l00030"></a>00030 <span class="comment">* Misra-C changes done </span>
83 <a name="l00031"></a>00031 <span class="comment">* -------------------------------------------------------------------- */</span>
84 <a name="l00032"></a>00032
85 <a name="l00033"></a>00033 <span class="preprocessor">#include "<a class="code" href="arm__math_8h.html">arm_math.h</a>"</span>
86 <a name="l00034"></a>00034
87 <a name="l00065"></a><a class="code" href="group___f_i_r__decimate.html#gab8bef6d0f6a26fdbfce9485727713ce5">00065</a> <span class="keywordtype">void</span> <a class="code" href="group___f_i_r__decimate.html#gab8bef6d0f6a26fdbfce9485727713ce5" title="Processing function for the Q15 FIR decimator.">arm_fir_decimate_q15</a>(
88 <a name="l00066"></a>00066 <span class="keyword">const</span> <a class="code" href="structarm__fir__decimate__instance__q15.html" title="Instance structure for the Q15 FIR decimator.">arm_fir_decimate_instance_q15</a> * S,
89 <a name="l00067"></a>00067 <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> * pSrc,
90 <a name="l00068"></a>00068 <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> * pDst,
91 <a name="l00069"></a>00069 uint32_t <a class="code" href="arm__fir__example__f32_8c.html#ab6558f40a619c2502fbc24c880fd4fb0">blockSize</a>)
92 <a name="l00070"></a>00070 {
93 <a name="l00071"></a>00071 <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> *pState = S-><a class="code" href="structarm__fir__decimate__instance__q15.html#a3f7b5184bb28853ef401b001df121047">pState</a>; <span class="comment">/* State pointer */</span>
94 <a name="l00072"></a>00072 <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> *pCoeffs = S-><a class="code" href="structarm__fir__decimate__instance__q15.html#a01cacab67e73945e8289075598ede14d">pCoeffs</a>; <span class="comment">/* Coefficient pointer */</span>
95 <a name="l00073"></a>00073 <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> *pStateCurnt; <span class="comment">/* Points to the current sample of the state */</span>
96 <a name="l00074"></a>00074 <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> *px; <span class="comment">/* Temporary pointer for state buffer */</span>
97 <a name="l00075"></a>00075 <a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a> *pb; <span class="comment">/* Temporary pointer coefficient buffer */</span>
98 <a name="l00076"></a>00076 <a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a> x0, c0; <span class="comment">/* Temporary variables to hold state and coefficient values */</span>
99 <a name="l00077"></a>00077 <a class="code" href="arm__math_8h.html#a5aea1cb12fc02d9d44c8abf217eaa5c6" title="64-bit fractional data type in 1.63 format.">q63_t</a> sum0; <span class="comment">/* Accumulators */</span>
100 <a name="l00078"></a>00078 uint32_t numTaps = S-><a class="code" href="structarm__fir__decimate__instance__q15.html#ac1e9844488ec717da334fbd4c4f41990">numTaps</a>; <span class="comment">/* Number of taps */</span>
101 <a name="l00079"></a>00079 uint32_t i, blkCnt, tapCnt, outBlockSize = blockSize / S-><a class="code" href="structarm__fir__decimate__instance__q15.html#aad9320284218b3aa378527ea518cf093">M</a>; <span class="comment">/* Loop counters */</span>
102 <a name="l00080"></a>00080
103 <a name="l00081"></a>00081 <span class="preprocessor">#ifndef ARM_MATH_CM0</span>
104 <a name="l00082"></a>00082 <span class="preprocessor"></span>
105 <a name="l00083"></a>00083 <span class="comment">/* Run the below code for Cortex-M4 and Cortex-M3 */</span>
106 <a name="l00084"></a>00084
107 <a name="l00085"></a>00085 <span class="comment">/* S->pState buffer contains previous frame (numTaps - 1) samples */</span>
108 <a name="l00086"></a>00086 <span class="comment">/* pStateCurnt points to the location where the new input data should be written */</span>
109 <a name="l00087"></a>00087 pStateCurnt = S-><a class="code" href="structarm__fir__decimate__instance__q15.html#a3f7b5184bb28853ef401b001df121047">pState</a> + (numTaps - 1u);
110 <a name="l00088"></a>00088
111 <a name="l00089"></a>00089 <span class="comment">/* Total number of output samples to be computed */</span>
112 <a name="l00090"></a>00090 blkCnt = outBlockSize;
113 <a name="l00091"></a>00091
114 <a name="l00092"></a>00092 <span class="keywordflow">while</span>(blkCnt > 0u)
115 <a name="l00093"></a>00093 {
116 <a name="l00094"></a>00094 <span class="comment">/* Copy decimation factor number of new input samples into the state buffer */</span>
117 <a name="l00095"></a>00095 i = S-><a class="code" href="structarm__fir__decimate__instance__q15.html#aad9320284218b3aa378527ea518cf093">M</a>;
118 <a name="l00096"></a>00096
119 <a name="l00097"></a>00097 <span class="keywordflow">do</span>
120 <a name="l00098"></a>00098 {
121 <a name="l00099"></a>00099 *pStateCurnt++ = *pSrc++;
122 <a name="l00100"></a>00100
123 <a name="l00101"></a>00101 } <span class="keywordflow">while</span>(--i);
124 <a name="l00102"></a>00102
125 <a name="l00103"></a>00103 <span class="comment">/*Set sum to zero */</span>
126 <a name="l00104"></a>00104 sum0 = 0;
127 <a name="l00105"></a>00105
128 <a name="l00106"></a>00106 <span class="comment">/* Initialize state pointer */</span>
129 <a name="l00107"></a>00107 px = pState;
130 <a name="l00108"></a>00108
131 <a name="l00109"></a>00109 <span class="comment">/* Initialize coeff pointer */</span>
132 <a name="l00110"></a>00110 pb = pCoeffs;
133 <a name="l00111"></a>00111
134 <a name="l00112"></a>00112 <span class="comment">/* Loop unrolling. Process 4 taps at a time. */</span>
135 <a name="l00113"></a>00113 tapCnt = numTaps >> 2;
136 <a name="l00114"></a>00114
137 <a name="l00115"></a>00115 <span class="comment">/* Loop over the number of taps. Unroll by a factor of 4. </span>
138 <a name="l00116"></a>00116 <span class="comment"> ** Repeat until we've computed numTaps-4 coefficients. */</span>
139 <a name="l00117"></a>00117 <span class="keywordflow">while</span>(tapCnt > 0u)
140 <a name="l00118"></a>00118 {
141 <a name="l00119"></a>00119 <span class="comment">/* Read the Read b[numTaps-1] and b[numTaps-2] coefficients */</span>
142 <a name="l00120"></a>00120 c0 = *<a class="code" href="arm__math_8h.html#a9de2e0a5785be82866bcb96012282248" title="definition to read/write two 16 bit values.">__SIMD32</a>(pb)++;
143 <a name="l00121"></a>00121
144 <a name="l00122"></a>00122 <span class="comment">/* Read x[n-numTaps-1] and x[n-numTaps-2]sample */</span>
145 <a name="l00123"></a>00123 x0 = *<a class="code" href="arm__math_8h.html#a9de2e0a5785be82866bcb96012282248" title="definition to read/write two 16 bit values.">__SIMD32</a>(px)++;
146 <a name="l00124"></a>00124
147 <a name="l00125"></a>00125 <span class="comment">/* Perform the multiply-accumulate */</span>
148 <a name="l00126"></a>00126 sum0 = __SMLALD(x0, c0, sum0);
149 <a name="l00127"></a>00127
150 <a name="l00128"></a>00128 <span class="comment">/* Read the b[numTaps-3] and b[numTaps-4] coefficient */</span>
151 <a name="l00129"></a>00129 c0 = *<a class="code" href="arm__math_8h.html#a9de2e0a5785be82866bcb96012282248" title="definition to read/write two 16 bit values.">__SIMD32</a>(pb)++;
152 <a name="l00130"></a>00130
153 <a name="l00131"></a>00131 <span class="comment">/* Read x[n-numTaps-2] and x[n-numTaps-3] sample */</span>
154 <a name="l00132"></a>00132 x0 = *<a class="code" href="arm__math_8h.html#a9de2e0a5785be82866bcb96012282248" title="definition to read/write two 16 bit values.">__SIMD32</a>(px)++;
155 <a name="l00133"></a>00133
156 <a name="l00134"></a>00134 <span class="comment">/* Perform the multiply-accumulate */</span>
157 <a name="l00135"></a>00135 sum0 = __SMLALD(x0, c0, sum0);
158 <a name="l00136"></a>00136
159 <a name="l00137"></a>00137 <span class="comment">/* Decrement the loop counter */</span>
160 <a name="l00138"></a>00138 tapCnt--;
161 <a name="l00139"></a>00139 }
162 <a name="l00140"></a>00140
163 <a name="l00141"></a>00141 <span class="comment">/* If the filter length is not a multiple of 4, compute the remaining filter taps */</span>
164 <a name="l00142"></a>00142 tapCnt = numTaps % 0x4u;
165 <a name="l00143"></a>00143
166 <a name="l00144"></a>00144 <span class="keywordflow">while</span>(tapCnt > 0u)
167 <a name="l00145"></a>00145 {
168 <a name="l00146"></a>00146 <span class="comment">/* Read coefficients */</span>
169 <a name="l00147"></a>00147 c0 = *pb++;
170 <a name="l00148"></a>00148
171 <a name="l00149"></a>00149 <span class="comment">/* Fetch 1 state variable */</span>
172 <a name="l00150"></a>00150 x0 = *px++;
173 <a name="l00151"></a>00151
174 <a name="l00152"></a>00152 <span class="comment">/* Perform the multiply-accumulate */</span>
175 <a name="l00153"></a>00153 sum0 = __SMLALD(x0, c0, sum0);
176 <a name="l00154"></a>00154
177 <a name="l00155"></a>00155 <span class="comment">/* Decrement the loop counter */</span>
178 <a name="l00156"></a>00156 tapCnt--;
179 <a name="l00157"></a>00157 }
180 <a name="l00158"></a>00158
181 <a name="l00159"></a>00159 <span class="comment">/* Advance the state pointer by the decimation factor </span>
182 <a name="l00160"></a>00160 <span class="comment"> * to process the next group of decimation factor number samples */</span>
183 <a name="l00161"></a>00161 pState = pState + S-><a class="code" href="structarm__fir__decimate__instance__q15.html#aad9320284218b3aa378527ea518cf093">M</a>;
184 <a name="l00162"></a>00162
185 <a name="l00163"></a>00163 <span class="comment">/* Store filter output, smlad returns the values in 2.14 format */</span>
186 <a name="l00164"></a>00164 <span class="comment">/* so downsacle by 15 to get output in 1.15 */</span>
187 <a name="l00165"></a>00165 *pDst++ = (<a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a>) (__SSAT((sum0 >> 15), 16));
188 <a name="l00166"></a>00166
189 <a name="l00167"></a>00167 <span class="comment">/* Decrement the loop counter */</span>
190 <a name="l00168"></a>00168 blkCnt--;
191 <a name="l00169"></a>00169 }
192 <a name="l00170"></a>00170
193 <a name="l00171"></a>00171 <span class="comment">/* Processing is complete. </span>
194 <a name="l00172"></a>00172 <span class="comment"> ** Now copy the last numTaps - 1 samples to the satrt of the state buffer. </span>
195 <a name="l00173"></a>00173 <span class="comment"> ** This prepares the state buffer for the next function call. */</span>
196 <a name="l00174"></a>00174
197 <a name="l00175"></a>00175 <span class="comment">/* Points to the start of the state buffer */</span>
198 <a name="l00176"></a>00176 pStateCurnt = S-><a class="code" href="structarm__fir__decimate__instance__q15.html#a3f7b5184bb28853ef401b001df121047">pState</a>;
199 <a name="l00177"></a>00177
200 <a name="l00178"></a>00178 i = (numTaps - 1u) >> 2u;
201 <a name="l00179"></a>00179
202 <a name="l00180"></a>00180 <span class="comment">/* copy data */</span>
203 <a name="l00181"></a>00181 <span class="keywordflow">while</span>(i > 0u)
204 <a name="l00182"></a>00182 {
205 <a name="l00183"></a>00183 *<a class="code" href="arm__math_8h.html#a9de2e0a5785be82866bcb96012282248" title="definition to read/write two 16 bit values.">__SIMD32</a>(pStateCurnt)++ = *<a class="code" href="arm__math_8h.html#a9de2e0a5785be82866bcb96012282248" title="definition to read/write two 16 bit values.">__SIMD32</a>(pState)++;
206 <a name="l00184"></a>00184 *<a class="code" href="arm__math_8h.html#a9de2e0a5785be82866bcb96012282248" title="definition to read/write two 16 bit values.">__SIMD32</a>(pStateCurnt)++ = *<a class="code" href="arm__math_8h.html#a9de2e0a5785be82866bcb96012282248" title="definition to read/write two 16 bit values.">__SIMD32</a>(pState)++;
207 <a name="l00185"></a>00185
208 <a name="l00186"></a>00186 <span class="comment">/* Decrement the loop counter */</span>
209 <a name="l00187"></a>00187 i--;
210 <a name="l00188"></a>00188 }
211 <a name="l00189"></a>00189
212 <a name="l00190"></a>00190 i = (numTaps - 1u) % 0x04u;
213 <a name="l00191"></a>00191
214 <a name="l00192"></a>00192 <span class="comment">/* copy data */</span>
215 <a name="l00193"></a>00193 <span class="keywordflow">while</span>(i > 0u)
216 <a name="l00194"></a>00194 {
217 <a name="l00195"></a>00195 *pStateCurnt++ = *pState++;
218 <a name="l00196"></a>00196
219 <a name="l00197"></a>00197 <span class="comment">/* Decrement the loop counter */</span>
220 <a name="l00198"></a>00198 i--;
221 <a name="l00199"></a>00199 }
222 <a name="l00200"></a>00200
223 <a name="l00201"></a>00201 <span class="preprocessor">#else</span>
224 <a name="l00202"></a>00202 <span class="preprocessor"></span>
225 <a name="l00203"></a>00203 <span class="comment">/* Run the below code for Cortex-M0 */</span>
226 <a name="l00204"></a>00204
227 <a name="l00205"></a>00205 <span class="comment">/* S->pState buffer contains previous frame (numTaps - 1) samples */</span>
228 <a name="l00206"></a>00206 <span class="comment">/* pStateCurnt points to the location where the new input data should be written */</span>
229 <a name="l00207"></a>00207 pStateCurnt = S-><a class="code" href="structarm__fir__decimate__instance__q15.html#a3f7b5184bb28853ef401b001df121047">pState</a> + (numTaps - 1u);
230 <a name="l00208"></a>00208
231 <a name="l00209"></a>00209 <span class="comment">/* Total number of output samples to be computed */</span>
232 <a name="l00210"></a>00210 blkCnt = outBlockSize;
233 <a name="l00211"></a>00211
234 <a name="l00212"></a>00212 <span class="keywordflow">while</span>(blkCnt > 0u)
235 <a name="l00213"></a>00213 {
236 <a name="l00214"></a>00214 <span class="comment">/* Copy decimation factor number of new input samples into the state buffer */</span>
237 <a name="l00215"></a>00215 i = S-><a class="code" href="structarm__fir__decimate__instance__q15.html#aad9320284218b3aa378527ea518cf093">M</a>;
238 <a name="l00216"></a>00216
239 <a name="l00217"></a>00217 <span class="keywordflow">do</span>
240 <a name="l00218"></a>00218 {
241 <a name="l00219"></a>00219 *pStateCurnt++ = *pSrc++;
242 <a name="l00220"></a>00220
243 <a name="l00221"></a>00221 } <span class="keywordflow">while</span>(--i);
244 <a name="l00222"></a>00222
245 <a name="l00223"></a>00223 <span class="comment">/*Set sum to zero */</span>
246 <a name="l00224"></a>00224 sum0 = 0;
247 <a name="l00225"></a>00225
248 <a name="l00226"></a>00226 <span class="comment">/* Initialize state pointer */</span>
249 <a name="l00227"></a>00227 px = pState;
250 <a name="l00228"></a>00228
251 <a name="l00229"></a>00229 <span class="comment">/* Initialize coeff pointer */</span>
252 <a name="l00230"></a>00230 pb = pCoeffs;
253 <a name="l00231"></a>00231
254 <a name="l00232"></a>00232 tapCnt = numTaps;
255 <a name="l00233"></a>00233
256 <a name="l00234"></a>00234 <span class="keywordflow">while</span>(tapCnt > 0u)
257 <a name="l00235"></a>00235 {
258 <a name="l00236"></a>00236 <span class="comment">/* Read coefficients */</span>
259 <a name="l00237"></a>00237 c0 = *pb++;
260 <a name="l00238"></a>00238
261 <a name="l00239"></a>00239 <span class="comment">/* Fetch 1 state variable */</span>
262 <a name="l00240"></a>00240 x0 = *px++;
263 <a name="l00241"></a>00241
264 <a name="l00242"></a>00242 <span class="comment">/* Perform the multiply-accumulate */</span>
265 <a name="l00243"></a>00243 sum0 += (<a class="code" href="arm__math_8h.html#adc89a3547f5324b7b3b95adec3806bc0" title="32-bit fractional data type in 1.31 format.">q31_t</a>) x0 *c0;
266 <a name="l00244"></a>00244
267 <a name="l00245"></a>00245 <span class="comment">/* Decrement the loop counter */</span>
268 <a name="l00246"></a>00246 tapCnt--;
269 <a name="l00247"></a>00247 }
270 <a name="l00248"></a>00248
271 <a name="l00249"></a>00249 <span class="comment">/* Advance the state pointer by the decimation factor </span>
272 <a name="l00250"></a>00250 <span class="comment"> * to process the next group of decimation factor number samples */</span>
273 <a name="l00251"></a>00251 pState = pState + S-><a class="code" href="structarm__fir__decimate__instance__q15.html#aad9320284218b3aa378527ea518cf093">M</a>;
274 <a name="l00252"></a>00252
275 <a name="l00253"></a>00253 <span class="comment">/*Store filter output , smlad will return the values in 2.14 format */</span>
276 <a name="l00254"></a>00254 <span class="comment">/* so downsacle by 15 to get output in 1.15 */</span>
277 <a name="l00255"></a>00255 *pDst++ = (<a class="code" href="arm__math_8h.html#ab5a8fb21a5b3b983d5f54f31614052ea" title="16-bit fractional data type in 1.15 format.">q15_t</a>) (__SSAT((sum0 >> 15), 16));
278 <a name="l00256"></a>00256
279 <a name="l00257"></a>00257 <span class="comment">/* Decrement the loop counter */</span>
280 <a name="l00258"></a>00258 blkCnt--;
281 <a name="l00259"></a>00259 }
282 <a name="l00260"></a>00260
283 <a name="l00261"></a>00261 <span class="comment">/* Processing is complete. </span>
284 <a name="l00262"></a>00262 <span class="comment"> ** Now copy the last numTaps - 1 samples to the start of the state buffer. </span>
285 <a name="l00263"></a>00263 <span class="comment"> ** This prepares the state buffer for the next function call. */</span>
286 <a name="l00264"></a>00264
287 <a name="l00265"></a>00265 <span class="comment">/* Points to the start of the state buffer */</span>
288 <a name="l00266"></a>00266 pStateCurnt = S-><a class="code" href="structarm__fir__decimate__instance__q15.html#a3f7b5184bb28853ef401b001df121047">pState</a>;
289 <a name="l00267"></a>00267
290 <a name="l00268"></a>00268 i = numTaps - 1u;
291 <a name="l00269"></a>00269
292 <a name="l00270"></a>00270 <span class="comment">/* copy data */</span>
293 <a name="l00271"></a>00271 <span class="keywordflow">while</span>(i > 0u)
294 <a name="l00272"></a>00272 {
295 <a name="l00273"></a>00273 *pStateCurnt++ = *pState++;
296 <a name="l00274"></a>00274
297 <a name="l00275"></a>00275 <span class="comment">/* Decrement the loop counter */</span>
298 <a name="l00276"></a>00276 i--;
299 <a name="l00277"></a>00277 }
300 <a name="l00278"></a>00278
301 <a name="l00279"></a>00279 <span class="preprocessor">#endif </span><span class="comment">/* #ifndef ARM_MATH_CM0 */</span>
302 <a name="l00280"></a>00280
303 <a name="l00281"></a>00281 }
304 <a name="l00282"></a>00282
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