8.4.2 SPI Signal Routing
The DLPC3478 device supports two SPI slave devices on the SPI0 interface, specifically, a serial flash and the DLPA200x or DLPA300x. This requires routing associated SPI signals to two locations while attempting to operate up to 36 MHz. Take special care to ensure that reflections do not compromise signal integrity. Follow these recommendations.
- Split the SPI0_CLK PCB signal trace from the DLPC3478 source to each slave device into separate routes as close to the DLPC3478 device as possible. Ensure that the SPI0_CLK trace length to each device are equal in total length.
- Split the SPI0_DOUT PCB signal trace from the DLPC3478 device source to each slave device into separate routes as close to the DLPC3478 device as possible. Ensure that the SPI0_DOUT trace length to each device are equal in total length (use the same strategy as listed for SPI0_CLK).
- Ensure the SPI0_DIN PCB signal trace from each slave device to the point where they intersect on the return to the DLPC3478 device are equal in length and as short as possible. Ensure that each slave device shares a common trace back to the DLPC3478 device.
- SPI0_CSZ0 and SPI0_CSZ1 need no special treatment because they are dedicated signals and drive only one device.