While I appreciate your willingness to advise me of my confusion, I assure you that I'm not confused in the least. I have JTAG tools on hand and use them almost daily. However, the only 805x-compatible devices I have in house that support are FPGA's into which I can load 805x IP if I so desire. Most of my 805x projects use standard 805x devices that were built before JTAG became popular and ubiquitous.

I have a module that plugs into an 8052 socket and contains a mappable UART/BRG and an easily configurable battery-backed RAM that lives in code space for the MCU. It currently has a debug monitor in it, the entry point of which is the default, but which can be mapped to nearly an 2KB boundary in the map. Top and bottom of the memory boundaries used by the target code are mapped out so the monitor doesn't/can't step on them except under certain circumstances, e.g. breakpoints set by the monitor. The hard code in the target system is copied to the code-space SRAM and accesses to the target-system-resident code are blocked once the code residing there is copied into the SRAM. Target-system RAM and I/O are undisturbed, with the exception that the module-resident UART/BRG has to live somewhere. I use a GAL to set its location, and that can easily be reprogrammed to suit my needs. It's not perfect, but does work in most cases wherein a drop-in for the 8052 is in use. I'm considering tailoring that somewhat more sleekly by using a DALLAS part that has a 64KB FLASH on board that is reprogrammable under resident software control. With that, I should be able to do more, albeit perhaps somewhat more clumsily. The clumsiness will be masked by its overall automation. This is somewhat like the in-circuit emulators I have, but they're much clumsier. They work, and I know their limitations and how to circumvent some of them, so I'm not likely to buy new ones.

That's where I think I can get more from a well-developed, fully-provisioned debugger debugger than from JTAG, which most of the target devices don't support.

Yes, an ICE hosted on a PC is a handy device, but less hardware, and, of course, less-obrusive hardware, is needed to support a resident debugger. Moreover, if I need more than one system to be operating at a time, I can simply insert a resident debugger and all I have to do is to install another debug monitor. I don't have to buy another multi-k-buck device from someone else and take my chances. That's why I want to use the debugger.

RE