5.4.1 Write Strobe Mapping

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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 5-10 and Figure 5-11. 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 5-4. 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 5-5. 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 5-6. 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 5-7. 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