Discussed internally with the author of the FS26 FAQ document.
The fact is that the FS26 uses a 32-bit SPI, with the following arrangement:
MOSI (Main Out, Secondary In) bits:
• Bit 31: Main or fail-safe registers selection
• Bit 30 to 25: Register address• Bit 24: Read/Write (For reading Bit 24 = 0; For writing Bit 24 = 1)
• Bit 23 to 8: Control bits
• Bit 7 to 0: Cyclic redundant check (CRC)
MISO (Main In, Secondary Out) bits:
• Bit 31-24: General device status
• Bits 23 to 8: Extended device status, or device internal control register content or device flags
• Bit 7 to 0: Cyclic redundant check (CRC)
BRs, Tomas