hi,

Pin Compatible? Somewhat beware of the SPI in 'S52.

Prahlad, AT89S52 does not have SPI for end user. This derivative may be in-system programmed via interface compatible with SPI. But it has not SPI for programming model: there is no SPI registers etc.
Try search its datasheet for the word "SPI" - it returns no result.

Regards,
Oleg