Hi All, I've a warning message : MULTIPLE CALL TO SEGMENT L15 The problem comes from 2 different ISRs that call the same function. What I dont understand is that both callers are ISRs and therfore the called function will not be called at the same time. I use keil 7.07 for an2131 cypress (ezusb), here is my code : #pragma NOAREGS static void Check_Data_Received(unsigned char data_received) { ... MIDI_In_Add_Buffer(data_received, &MIDI_In_From_Con); ... } static void MIDI_In_Add_Buffer(unsigned char data_in, Midi_In_Struct *midi_struct) { ... } #pragma AREGS static void serial_port_0_isr (void) interrupt COM0_VECT using 1 { BYTE data_received; ... Check_Data_Received(data_received); ... } void ISR_Ep2out(void) interrupt 0 { .. MIDI_In_Add_Buffer(OUT2BUF[index+frame+1], &MIDI_In_From_Usb); } The warning is as follow : *** WARNING L15: MULTIPLE CALL TO SEGMENT SEGMENT: ?PR?_MIDI_IN_ADD_BUFFER?ITR CALLER1: ?PR?SERIAL_PORT_0_ISR?ITR CALLER2: ?PR?USB_JUMP_TABLE?USBJT Any help greatly appreciated