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Receive double bytes in SPI slave for VNC2 at somtimes

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Yvonne:
Hello,

I use the VNC2 as SPI slave of V2DIP1-32 board, which receives data from C232HM-DDHSL-0 as SPI master.

Now I can only receive the complete data bytes when setting the transmitting frequency of SPI master at around 300KHz or below (Here the sent data bytes are 0x10, 0x20, 0x30, ..., 0xF0), which can be shown in the first attached figure.

When the transmit frequency of SPI master is faster than 300KHz (for example 350KHz or larger than 350KHz such like 400KHz), I will receive the data string with double or triple bytes in some bytes as shown in second attached figure. The frequency of CPU for VNC2 as SPI slave is set to 48MHz in code.

Are there any other methods or suggestions to get faster frequency for SPI master sending data but not cause the data bytes be repeatly transmitted (i.e. I receive double or triple bytes in MISO)? Is this related to the tx FIFO size of the hardware of VNC2? How to adjust the tx FIFO size?

Or any suggestions or directions are appreciated.
Thanks in advanced!
Yvonne

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