Write Strobe Mapping

Mapping of the write strobe signal WSTRB to write data WDATA is done on a phased basis, by mapping WDATA to the QDR data bus D, as shown in Figure 7, page 12 and Figure 8, page 13. However, it is also aligned to BWSx_N signals on the QDR interface as follows. Note that the following example is for SRAM_DWIDTH of 36, or x36 mode.

Table 1. WSTRB to BWS Mapping
WSTRB Index BWS Index
7:0 0
15:8 1
23:16 2
31:24 3

Within each WSTRB byte, each bit corresponds to a clock cycle (phase) and either rising or falling edge. A complete mapping for write data bus WDATA to WSTRB is listed in the following tables, for x36, x18, and x9 modes.

Table 2. Write Data to Write Strobe Mapping (x36)
WSTRB_MAPPING_INDEX WDATA INDEX RISING/FALLING CLOCK CYCLE
0 0 1 2 3 4 5 6 7 8 RISING 1
8 36 37 38 39 40 41 42 43 44 FALLING 1
16 72 73 74 75 76 77 78 79 80 RISING 2
24 108 109 110 111 112 113 114 115 116 FALLING 2
1 144 145 146 147 148 149 150 151 152 RISING 3
9 180 181 182 183 184 185 186 187 188 FALLING 3
17 216 217 218 219 220 221 222 223 224 RISING 4
25 252 253 254 255 256 257 258 259 260 FALLING 4
2 9 10 11 12 13 14 15 16 17 RISING 1
10 45 46 47 48 49 50 51 52 53 FALLING 1
18 81 82 83 84 85 86 87 88 89 RISING 2
26 117 118 119 120 121 122 123 124 125 FALLING 2
3 153 154 155 156 157 158 159 160 161 RISING 3
11 189 190 191 192 193 194 195 196 197 FALLING 3
19 225 226 227 228 229 230 231 232 233 RISING 4
27 261 262 263 264 265 266 267 268 269 FALLING 4
4 18 19 20 21 22 23 24 25 26 RISING 1
12 54 55 56 57 58 59 60 61 62 FALLING 1
20 90 91 92 93 94 95 96 97 98 RISING 2
28 126 127 128 129 130 131 132 133 134 FALLING 2
5 162 163 164 165 166 167 168 169 170 RISING 3
13 198 199 200 201 202 203 204 205 206 FALLING 3
21 234 235 236 237 238 239 240 241 242 RISING 4
29 270 271 272 273 274 275 276 277 278 FALLING 4
6 27 28 29 30 31 32 33 34 35 RISING 1
14 63 64 65 66 67 68 69 70 71 FALLING 1
22 99 100 101 102 103 104 105 106 107 RISING 2
30 135 136 137 138 139 140 141 142 143 FALLING 2
7 171 172 173 174 175 176 177 178 179 RISING 3
15 207 208 209 210 211 212 213 214 215 FALLING 3
23 243 244 245 246 247 248 249 250 251 RISING 4
31 279 280 281 282 283 284 285 286 287 FALLING 4
(1) The mapping is not sequential. First bit of write_strobe corresponds to the first 9 wdata bits. The second bit does not correspond to the next 9 wdata bits.  
Table 3. Write Data to Write Strobe Mapping (x18)
WSTRB_MAPPING_INDEX WDATA INDEX RISING/FALLING CLOCK CYCLE
0 0 1 2 3 4 5 6 7 8 RISING 1
8 36 37 38 39 40 41 42 43 44 FALLING 1
1 72 73 74 75 76 77 78 79 80 RISING 2
9 108 109 110 111 112 113 114 115 116 FALLING 2
2 9 10 11 12 13 14 15 16 17 RISING 3
10 45 46 47 48 49 50 51 52 53 FALLING 3
3 81 82 83 84 85 86 87 88 89 RISING 4
11 117 118 119 120 121 122 123 124 125 FALLING 4
4 18 19 20 21 22 23 24 25 26 RISING 1
12 54 55 56 57 58 59 60 61 62 FALLING 1
5 90 91 92 93 94 95 96 97 98 RISING 2
13 126 127 128 129 130 131 132 133 134 FALLING 2
6 27 28 29 30 31 32 33 34 35 RISING 3
14 63 64 65 66 67 68 69 70 71 FALLING 3
7 99 100 101 102 103 104 105 106 107 RISING 4
15 135 136 137 138 139 140 141 142 143 FALLING 4
(1) The mapping is not sequential. First bit of write_strobe corresponds to the first 9 wdata bits. The second bit does not correspond to the next 9 wdata bits.  
Table 4. Write Data to Write Strobe Mapping (x9)
WSTRB_MAPPING_INDEX WDATA INDEX RISING/FALLING CLOCK CYCLE
0 0 1 2 3 4 5 6 7 8 RISING 1
1 36 37 38 39 40 41 42 43 44 FALLING 2
2 9 10 11 12 13 14 15 16 17 RISING 3
3 45 46 47 48 49 50 51 52 53 FALLING 4
4 18 19 20 21 22 23 24 25 26 RISING 1
5 54 55 56 57 58 59 60 61 62 FALLING 2
6 27 28 29 30 31 32 33 34 35 RISING 3
7 63 64 65 66 67 68 69 70 71 FALLING 4