Hi Dan, What we do here to get around this problem, is to use the Motorola SDK Interrupt Dispatcher and a "Normal" interrupt. How to do this is described in several of my earlier postings to the motoroladsp discussion group. The SDK Interrupt Dispatcher saves and restores everything, including the Hardware Stack. If you don't want to use the SDK Interrupt Dispatcher, you can save and restore the lc and la registers and the Hardware Stack yourself, please see my message "RE: [motoroladsp] Interrupt stack pointer corruption" that I posted on September 23, 2002, at 12:37pm. It explains what you need to do. I am posting this message to the motoroladsp discussion group, as I think other members could find this information to be useful. Best regards, Art Johnson Senior Systems Analyst PMC Prime Mover Controls Inc. 3600 Gilmore Way Burnaby, B.C., Canada V5G 4R8 Phone: 604 433-4644 FAX: 604 433-5570 Email: http://www.pmc-controls.com -----Original Message----- From: Danknick, Dan [mailto:] Sent: Thursday, November 14, 2002 6:03 PM To: Art Johnson Subject: HW stack Hi Art, Are you aware of any replacement math library routines from Metrowerks that are safe to use in an ISR? I just got bit by a HW stack overflow in ARTDIVU16UZ.asm - seems the ISR "wrapper" doesn't bother saving the HW stack. I saw you posted new versions of the memcpy() stuff to the Yahoo group that didn't use DO loops, just wondering if you dealt with math as well. Thanks and best regards, Dan Danknick Celerity R&D