Why are you not developing your software directly on the controller? Downloading into the AT89C8252's Flash is very convenient by using ISP. I have included drivers's for the AT89S8252's EEProm in my uC/51 Compiler. The 8 kB Demo limit is not less than the 8252's maximum code size. So you can completely use the demo (for non commercial-use). You can find a link to uC/51 in 8052.com's online-shop ;-)
Regards,
Jürgen.

PS.: In a short time I'll have finished the new Flash-Debugger, this means you can debug uC/51 C programs on almost any system! On some controllers with IAP (In-Application-Programming) like Atmel's RD's, Analog's ADuC's, Texas MSC, ... etc. even the manufacturer's original downloader will be obsolete....