ya i think most of codes are compatiable… but the other way round i think may not be i mean the code for c52 will work for s52 series but the codes for s52 may not work for c52….
for example s series 8051 controller contains inbuit SPI(serial peripherial interface), if you use if you use that in your code them it will not be compatialbe with c52 series since it doesn’t contains any inbilt SPI…