Config of SPI MOSI Pin level at idle for RL78/F14

I'm using the RL78 R5F10PGG (48-pin) SPI module.

Everything behaves as expected except that the SDO line seems to have an idle state of low so that the SDO pin is held low whenever data is not transmitted.  I would like the SDO pin to remain high unless I push out a '0' from the SPI TX.

The SDO idle state seems to be undefined in documentation.  Can the SPI module be set up to create what I want?