HC9S12 SPI Interface to NXP SC16IS760 UART

[KH_SRNL]

Has anyone interfaced the 9S12 to a NXP SC16IS760 SPI UART?  I've built a test board (with logic level translators to go from a 5 Volt 9S12 to the 3.3V 16IS760) and can send / receive SPI data, but have no idea what responses I should expect from the UART device when sending configuration commands.  The NXP chip always replies with 0x00 and after completing the configuration I am not able to successfully send data through the UART (via the SPI bus) to the TTL level serial outputs.

Any help (and code) would be much appreciated.

[bigmac]

Hello,

It's a bit difficult to diagnose your problem unless you post the SPI communications function code that you are using.

It would seem that the SPI initialisation should configure CPOL = 0; CPHA = 1 to suit the UART device, and you will need to explicitly control the CS output signal, which would be derived from GPIO.

Since the MISO connection appears that it may be high-Z for some of the time, an external pullup resistor might be applied to this pin (at the input of the voltage translation buffer).  I assume that the voltage translation buffers are of the non-inverting type.

To test the SPI communications, it should be possible to write a non-zero value to one of the configuration registers, and then read back the stored register value to confirm the write.

Regards,

Mac