How to control the Watchdog present in L99ASC03 via SPI from Rh850 MCU

[SanBha]

In our Project CAN communication isestablished via CANtrcv TJA1145, the INH is triggering the wakeup to L99ASC03, then the watchdog present in L99 is triggering to switchof MCU so I need to control the Watchdog via SPI by writing the value to its register as in L99ASC03 Datasheet shown below, could you please support how shall I implement this to send via SPI.

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[Peter BENSCH]

Welcome ​@SanBha, to the community!

As the L99ASC03 already has NRND status (Not Recommended for New Designs), you should not start a new project with it, as it will soon be discontinued. However, the L99ASC03G is a drop-in replacement.

To service the L99ASC03G watchdog via SPI, write Device Control Register 1 at address 0x01 and toggle bit 0 (WDTRIG) on each service. The device uses a 16-bit ST-SPI frame: 2-bit opcode + 6-bit address + 8-bit data, with Write opcode = 00, and SPI mode CPOL=0, CPHA=0. You could keep a local copy of Register 0x01 in the MCU, invert WDTRIG each time, and transmit the full byte in a write frame. Please ensure you respect the watchdog window timing and send exactly 16 clock cycles per SPI frame.

Hope that helps?

Regards
/Peter