DS90UH948-Q1 Datasheet, PDF (27/91 Pages) Texas Instruments – FPD-Link III to OpenLDI Deserializer

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SERIALIZER
SS
SPLK
MOSI
D0
MISO
DS90UH948-Q1
SNLS473A – OCTOBER 2014 – REVISED JANUARY 2016
D1
RD0
RD1
SS
DESERIALIZER
SPLK
D0
MOSI
MISO
RD0
RD1
Figure 20. Forward Channel SPI Read
8.3.10.3 Reverse Channel SPI Operation
In Reverse Channel SPI operation, the Deserializer samples the Slave Select (SS), SPI clock (SCLK) into the
internal oscillator clock domain. In addition, upon detection of the active SPI clock edge, the Deserializer
samples the SPI data (MOSI). The SPI data samples are stored in a buffer to be passed to the Serializer over
the back channel. The Deserializer sends SPI information in a back channel frame to the Serializer. In each
back channel frame, the Deserializer sends an indication of the Slave Select value. The Slave Select should be
inactive (high) for at least one back-channel frame period to ensure propagation to the Serializer.
Because data is delivered in separate back channel frames and buffered, the data may be regenerated in
bursts. The following figure (Figure 21) shows an example of the SPI data regeneration when the data arrives in
three back channel frames. The first frame delivered the SS active indication, the second frame delivered the
first three data bits, and the third frame delivers the additional data bits.
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