MHC 1.07 (1_07_01) cannot set REFCLK as SPI MCLK on PIC32MX270F256B (oVo)

Hi all, As described in the PIC32MX270F256B and in the specific SPI (section 23) datasheets, the SPI baud rate generator can take REFCLK or PBCLK as Master Clock regarding to the MCLKSEL bit of SPIxCON register.But it seems impossible to set the REFCLK as..