Problem with interrupt on JTAG UART

Dear all,

I have a problem with the JTAG UART and interrupt. My aim is to use the JTAG UART to send and receive information from a PC. I want to activate the read interrupt but not the write one, i.e. I want an interrupt when I receive something, but I want to write just when I want (because it is not regular).

My problem is that the write interrupt is always activated. In my program, I just send a message to the PC, and the program goes to the ISR. I do not understand why since I activate only the bit RE in the control register. In the ISR, I read the control register, and it gives me the value 0x00402603. Which means there are 64 spaces available in the write FIFO, the interrupt was activated by writing, and the interrupts are enable on writing and reading.

If you can tell me why I have this problem. And in the Quartus Handbook volume 5, it is said "Programmers using the HAL API never access the JTAG UART core directly via its registers." But in this case how can we choose which interrupt we want to use ?

Thanks in advance

Jérôme

FILE * lcd;
void handleJTAGInterrupt (void* context, alt_u32 id)
{
    unsigned int controlRegister;
    
    controlRegister = IORD_ALTERA_AVALON_JTAG_UART_CONTROL(JTAG_UART_BASE);
    fprintf(lcd, "\r%8X", controlRegister);
}
int main (void)
{
    IOWR_ALTERA_AVALON_JTAG_UART_CONTROL(JTAG_UART_BASE, 0x01);                 // Active the read interrupt on JTAG
    alt_irq_register(JTAG_UART_IRQ, 0, handleJTAGInterrupt);                    // Register the ISR for JTAG
    IOWR_ALTERA_AVALON_PIO_DATA(LED_PIO_BASE, 0xEE);
    lcd = fopen("/dev/lcd", "w");                                               // Open the LCD device
    printf("test\n");                                                           // Display text on computer (Nios II IDE console)
    while(1);
}