DS90UB947-Q1 Datasheet, PDF (21/81 Pages) Texas Instruments – 1080p OpenLDI to FPD-Link III Serializer

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DS90UB947-Q1
SNLS454 – NOVEMBER 2014
8.3.11 SPI Communication
The SPI Control Channel utilizes the secondary link in a 2-lane FPD-Link III implementation. Two possible
modes are available, Forward Channel and Reverse Channel modes. In Forward Channel mode, the SPI Master
is located at the Serializer, such that the direction of sending SPI data is in the same direction as the video data.
In Reverse Channel mode, the SPI Master is located at the Deserializer, such that the direction of sending SPI
data is in the opposite direction as the video data.
The SPI Control Channel can operate in a high speed mode when writing data, but must operate at lower
frequencies when reading data. During SPI reads, data is clocked from the slave to the master on the SPI clock
falling edge. Thus, the SPI read must operate with a clock period that is greater than the round trip data latency.
On the other hand, for SPI writes, data can be sent at much higher frequencies where the MISO pin can be
ignored by the master.
SPI data rates are not symmetrical for the two modes of operation. Data over the forward channel can be sent
much faster than data over the reverse channel.
Note: SPI cannot be used to access Serializer / Deserializer registers.
8.3.11.1 SPI Mode Configuration
SPI is configured over I2C using the High-Speed Control Channel Configuration (HSCC_CONTROL) register
0x43 on the deserializer. HSCC_MODE (0x43[2:0]) must be configured for either High-Speed, Forward Channel
SPI mode (110) or High-Speed, Reverse Channel SPI mode (111).
8.3.11.2 Forward Channel SPI Operation
In Forward Channel SPI operation, the SPI master located at the Serializer generates the SPI Clock (SPLK),
Master Out / Slave In data (MOSI), and active low Slave Select (SS). The Serializer oversamples the SPI
signals directly using the video pixel clock. The three sampled values for SPLK, MOSI, and SS are each sent on
data bits in the forward channel frame. At the Deserializer, the SPI signals are regenerated using the pixel
clock. In order to preserve setup and hold time, the Deserializer will hold MOSI data while the SPLK signal is
high. In addition, it delays SPLK by one pixel clock relative to the MOSI data, increasing setup by one pixel
clock.
SERIALIZER
SS
SPLK
MOSI
D0
D1
D2
D3
DN
SS
DESERIALIZER
SPLK
MOSI
D0
D1
D2
D3
DN
Figure 17. Forward Channel SPI Write
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