Debugging AT89C51RD2

Look in the Datasheet to see what debug support (if any) it provides.

With no on-chip debug, you'll just have to resort to old-school techniques like printf & toggling IO pins.

The Simulator might be helpful in some cases.

Maybe use a device with on-chip debug while debugging, and port to a "non-debug" chip when done?

Look in the Datasheet to see what debug support (if any) it provides.

With no on-chip debug, you'll just have to resort to old-school techniques like printf & toggling IO pins.

The Simulator might be helpful in some cases.

Maybe use a device with on-chip debug while debugging, and port to a "non-debug" chip when done?

Andrew should have mentioned that there are now 100's of MODERN '51 devices with built-in debug e.g. SiLabs. re Old School, there is/was such a thing as an ICE, you may fins one on e-bay or somewhere, Make sure you get the software also if you buy one.

www.ebay.com/.../273534117910

Not clear if that would provide functionality via an RS232 terminal

Perhaps whomever made the design decision to use the part can provide direction?