Uart data ready

Ah aH :-)

(You can enclose your code with

 ... 

)

Try

if (IORD_ALTERA_AVALON_UART_STATUS(UART_BASE) & ALTERA_AVALON_UART_STATUS_RRDY_MSK) // be coherent
{
status = IORD_ALTERA_AVALON_UART_STATUS(UART_BASE); // status=64 means "TRDY=1" and that is normal.
// IOWR(UART_BASE,0x01, status);
IOWR_ALTERA_AVALON_UART_TXDATA(UART_BASE,status); // status is 16-bit wide , OK
}

For reference , http://www.altera.com/literature/ug/ug_embedded_ip.pdf (UART CORE REGISTER MAP en page 79)

I may laugh if since the beginning, your are looking for the wrong register bit : trdy instead of rrdy :-d

My teacher would says "Fatal Error" and give 0 point to the whole exam ! :-)

On an other side,

# include "system.h" // doesn't mean that system.h matches to SOPC, even if system.h exists and makes no software build error.

You could have an working system.h but very old and not matching.