Hello Jesus,

you must not initialize the stack, since the compiler
does it already.
Your program was correct and must work fine
with any OTP device.

But on using external ROM/RAM it can be, you
use also the WR and RD signals (shared with P3).

So try better using P1.
Also you can use all other P3 port pins if RD and WR always
was hold in high state.
E.g.:

P3 = 0xC0 | 0x55;
P3 = 0xC0 | 0xAA;

Watch also all other alternative port functions
(e.g. RXD, TXD on using the UART).


Peter