Hi,
there's a lot of differences from software point of view (modules, interrupts, memory map...) but it's compatible in case of hardware. There's no difference in pinout (I means in supply voltages, GNDs...).
The only visible difference is: when the device is empty, 0N47T is periodically reset after power up. The device comes out of reset each about 120us and after very short time the reset is triggered again because because there's no valid reset vector.
There's Boot ROM on 0N77P which is executed after reset, so it's just hanging somewhere in software endless loop (that means reset is not triggered). Boot ROM has been removed on 0N47T.
Regards,
Lukas