If you want a good ICE solution for not only this chip but any other, and I mean any other MCS51 chip, take a look at what Flash Designs have to offer at www.flash.co.uk. They have a very neat solution combining the best of hardware emulator and a very small non-intrusive background debugger. Their Snapshot mode looks like the ideal way of debugging real-time systems that must run in 99.9999999% real-time.