1. Power-up sequence for programming:
Apply power between VCC and GND pins
Set RST and XTAL1 to GND
2. Set pin RST to
Set pin P3.2 to
3. Apply the appropriate combination of logic
levels to pins P3.3, P3.4, P3.5, P3.7 to select one of the programming operations
shown in the PEROM Programming Modes table.......
[the above edited due to garbage from cut-and-paste - read the datasheet.]

.... and by the above it is clear that you chip is not ISP or IAP, but merely "serially programmable"

why not choose a chip that can do ISP? I imagine your interest in switching package is space.

There is another way. I have seen SOIC connectors (do not ask where), if you use one such and program the chips before soldering them in.

Erik