How can I get the SPI Chip Select line on the BF537 EZ-Kit to stay low for entire command?

[jmburns]

I'm trying to write an SD Card driver which uses the SPI bus on the Blackfin 537 EZ-Kit.  Commands to the SD Card are 6 Bytes in length, and the Chip Select should be set low for the length of the command.  However, I can only configure the SPI bus to stay low for 8 or 16 bits (1 or 2 bytes) before it momentarily bounces high, then gets pulled low again for the next 1 or 2 bytes.  Is there any way to get the Chip Select to stay low for the entire 6 bytes?

Thanks,
Jason