Is that any one can help me on ISP for AT89S54
Hello, Atmel provides the list of produced devices here: http://www.atmel.com/dyn/products/devices.asp?family_id=604 As about that datasheet you posted link to, so it seems like a fake due many details, for example: - Atmel has never produced AT89Sxx with software bootloader; all AT89Sxx have ISP-via-SPI only; - SPI is described but not indicated at pinout; - block diagram seems incomplete; - all the description is very similar to AT89C51RB2,RC2 and RD2, read here: http://www.atmel.com/dyn/products/product_card.asp?part_id=3044" Drop to use derivatives which are not public indicated by Atmel itself at their site. Regards, Oleg