SPI slave chip select problem

Aduc7020 spi in slave mode, CS pin p1.7 grounded. Then, after reset, no data available on MISO. If CS not grounded during reset, but grouded manualy after reset - all is ok. Can I ground CS pin?

Thanks.

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  • If you do not use the /CS signal you have no control about start and stop of a frame.

    You may use a GPIO from the ADuC7021 itself to toggle the /CS, but still there is a potential problem if you have noise on the SPICLK. This can cause a extra bit shift on the SPI and without a more complex workaround using the PLA, the only solution is to do a SW-RESET of the whole part to resolve this. So the other direction - use ADuC7021 as Master is more solid.

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  • If you do not use the /CS signal you have no control about start and stop of a frame.

    You may use a GPIO from the ADuC7021 itself to toggle the /CS, but still there is a potential problem if you have noise on the SPICLK. This can cause a extra bit shift on the SPI and without a more complex workaround using the PLA, the only solution is to do a SW-RESET of the whole part to resolve this. So the other direction - use ADuC7021 as Master is more solid.

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