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Commit | Line | Data |
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e7a4e115 GS |
1 | ------------------------------------------------------------------------ |
2 | SQI communication (multi-I/O SPI) | |
3 | ------------------------------------------------------------------------ | |
4 | ||
5 | This capture demonstrates SQI communication, which is a form of SPI data | |
6 | exchange where transmitters use multiple I/O data lines in parallel to | |
7 | communicate the same amount of data in fewer clock cycles. | |
8 | ||
9 | In contrast to e.g. QuadSPI flash memory chips which may change the data | |
10 | line count or clock scheme several times within a transaction, SQI keeps | |
11 | the clock and the number of data lines used by the transmitter consistent | |
12 | across the full length of the SPI transaction. Only the direction of data | |
13 | lines could change, when e.g. a master first transmits a request which | |
14 | the slave then responds to, while both use the same number of data lines. | |
15 | Full duplex communication as with the traditional MISO/MOSI scheme is | |
16 | not possible with SQI. | |
17 | ||
18 | ||
19 | Logic analyzer setup | |
20 | -------------------- | |
21 | ||
22 | The capture was taken at a samplerate of 100MHz. | |
23 | ||
24 | Probe SPI | |
25 | ---------------------------- | |
26 | 2 SCK (clock) | |
27 | 3 CS (select) | |
28 | 4 IO0 (data, LSB) | |
29 | 5 IO1 | |
30 | 6 IO2 | |
31 | 7 IO3 (data, MSB) | |
32 | ||
33 | ||
34 | sqi-four-data-lines-one-transfer.sr | |
35 | ----------------------------------- | |
36 | ||
37 | This capture uses four I/O data lines. Data gets sampled at the rising | |
38 | clock edge (single data rate). Data is sent in MSB first order. The SPI | |
39 | transaction's data byte sequence is: | |
40 | ||
41 | 80 00 00 10 22 42 4f 4f 54 00 80 00 00 a8 85 77 00 20 4e 00 00 | |
42 | ||
43 | ||
44 | sqi-four-data-lines-three-transfers.sr | |
45 | -------------------------------------- | |
46 | ||
47 | This capture was constructed from the above single-transfer example | |
48 | capture. The SPI transfer is repeated three times. |