SC16IS750 software reset does not work in SPI mode?

[shinoda]

I have a software that drives an SC16IS750 in both I2C and SPI modes. The SC16IS750 works great in both modes except for one single problem. That is, "SC16IS750 does not seem to respond to software reset bit (SRESET) written to  IOControl[3] in SPI mode".

After writing 1 to this bit, all registers remain unchanged.

It does respond to the very same process in I2C mode, and registers are initialized as described in the "7.4.1 Hardware reset, Power-On Reset (POR) and software reset".

Have any information on this phenomenon?

[shinoda · Accepted solution]

Tomas,

Thanks for the comment.

Actually, the problem was self solved.

It was caused by the wrong bus mode. The chip should have been operated with CPOL=0 and CPHA=0 (aka mode 0), but my driver was using CPOL=1 and CPHA=1 (aka mode 3).

It's super amazing that rest of the driver works perfectly with mode 3, sending and writing continuously using fifo; the IOControl register was the only register I couldn't write/read correctly.

[TomasVaverka]

Hi Yoichi,

I have not heard of such a problem before and I am asking our product group to comment on this.

Meanwhile, could you please post here a screenshot illustrating the SPI transfer when writing to the IOControl register?

Regards,

Tomas