UART max speed

In Quartus II v6.0 Handbook -> embedded peripherals.

You could find this for UART baudrate configuration :

divisor=int((clok freq/baudrate)+0.5)

baudrate = clock freq / (divisor +1)

You have to determine max clock freq of your design to determine max baud rate

How to modify baudrate :

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According to your clock freq and the baudrate you want, write into the divisor :

IOWR_ALTERA_AVALON_UART_DIVISOR(uart_base_addr, new_divisor);

don't forget to allow modification of divisor in SOPC Builder

you can also read your divisor with IORD_ALTERA_AVALON_UART_DIVISOR..

You don't need to open a file descriptor on the uart IP device

example :

clock freq : 50Mhz

baudrate : 921600 bds

divisor = 54