NEC Renesas V850/SC1 User Manual page 335

CHAPTER 11 SERIAL INTERFACE FUNCTION
If the transfer bit length is set to other than 16 bits, when setting data to the shift register, be sure to align data
from the lowest bit, regardless of whether the first transfer bit is MSB or LSB. Any data can be set to the unused
higher bits, but in this case the data received after a serial transfer operation becomes 0.
Figure 11-6. When Transfer Bit Length Other Than 16 Bits Is Set
(a) When transfer bit length is 10 bits and MSB first
SO4
SI4
15 10 9 0
Fixed to 0
(b) When transfer bit length is 12 bits and LSB first
SI4 SO4
15 12 11 0
Fixed to 0
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User's Manual U15109EJ3V0UD