SPI error in ADuC7024

Now I want to use SPI of ADuC7024 to extend a LCD.But I fail to write any data to SPITX which is SPI's transmitting register.Who could help me?Thank you!

There is the beginning code.
int main(void)
{
GP1CON = 0x02220000;
SPICON = 0x1B0F;
SPIDIV = 0x0F;
SPITX = 0xA2; // can't write 0xA2 to
// SPITX
………………
………………
}