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N720 OpenLinux
Hardware User Guide
Copyright © Neoway Technology Co., Ltd
40
SPI_MISO_BLSP2
85
DI
Master input
Leave this pin floating if it is not used.
SPI_MOSI_BLSP2
86
DO Master output
Leave this pin floating if it is not used.
SPI_CS_N_BLSP2
87
DO Chip select
Leave this pin floating if it is not used.
The SPI interface operates at 1.8V. It supports a maximum frequency of 50 MHz and only host mode.
Figure 3-33 and table show the SPI connection.
Figure 3-33 SPI connection
SPI_MOSI
SPI_CS_N
SPI_CLK
N720 module
(host)
SPI_MISO
MOSI
MISO
CLK
CS
SPI device
(device)
Schematic Design Recommendations
Note the SPI signal direction.
If the levels of slave SPI device and N720 OpenLinux do not match, add a level shifting circuit.
Refer to Figure 3-20 if the SPI speed does not exceed 20 MHz. Select other high-speed level
shifting chipsets if the speed exceeds 20 MHz.
PCB Design Guidelines
Do not cross other traces if possible. If crossing is inevitable, route the SPI traces perpendicular
to other traces.
Keep SPI traces far away from areas that might introduce ESD.
Surround signal traces with ground.
Figure 3-34 and Table 3-9 shows SPI timing and parameters respectively.