#SC900717 SPI Register address issue?

Mooang — Fri, 24 Apr 2026 04:36:54 GMT

Hello,

I am currently working with the SC900717AE device. I am implementing SPI communication, but I have some doubts regarding whether the actual register behaviors perfectly match the descriptions in the datasheet.

I have two main points of confusion:

1. Unexpected value in Message 18 (AR) When I read Message 18, the returned AR[7:0] value was 197 (0xC5). According to the datasheet, the last step of the ALU Checker calculation is dividing by 4. Within an 8-bit calculation context, deriving 197 (which would imply a previous value around 197 * 4 = 788) doesn't seem mathematically possible. This is my first point of suspicion.

2. Non-zero values in Messages 24, 25, and 26 Secondly, when reading Messages 24, 25, and 26, my understanding from the datasheet is that the 10 LSBs should all be read as 0. However, during actual SPI communication, unexpected non-zero values are being returned in those bits.

I would deeply appreciate it if anyone could explain these phenomena or point out if I am misinterpreting the datasheet.

Thank you, and have a great day.

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#SC900717 SPI Register address issue?