Mirko, The only PCI function available from the uEngine is the DMA function. Doorbell registers are not accessible from the uEngines. If you want to generate an interrupt to the StrongARM, you can use IREG. That's the only source of interrupts from the uEngine to the control plan. Regards, Carlo -----Original Message----- From: Mirko Benz [mailto:benz@mephisto.inf.tu-dresden.de] Sent: Friday, March 01, 2002 8:47 AM To: ixp1200@CS.Princeton.EDU Subject: [ixp1200] doorbell interrupt? Hi, Is it possible to write to the doorbell register from uEngines? Or are there other opportunities to generate interrupts from there? Regards, Mirko