Cypress ez-usb and interrupts

Hi all,

I'm dealing with a cy7c68013a and the framework cypress provide. The fw use a jump table for usb interrupt but I've to add some ISR for INT0 and serial comm.

Do I need a .a51 file like this?

;INT0 vector handler
EXTRN CODE (ISR_INT0)
CSEG AT 0003H LJMP ISR_INT0
END

And inside C code:

void ISR_INT0(void) interrupt 0
{...}

What does mean "interrupt 0"?
I can't find documentation about syntax of ISR ...
fw already uses "interrupt 0" do I've to use 1?

Thanks a lot