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