Although I don't know assembly of 8052 I will try to have a go at this.
first look I guess that r0 is a pointer to some data you need to modify so your routine must do some sort of conversion on some data.
Looking further down you keep multiplying each digit by 100 decimal 64h then manipulating nibbles.
So my quick guess is that you are converting from binary to a BCD.
When I have time I will run your code in the simulator and find exactly what it does.
Mahmood