write_byte:

clr cs
push acc
mov a,dph
rrc a
mov a,#write
mov a8,c
call masterio
mov a,dpl
call masterio
pop acc
call masterio
setb cs
ret

Where do you put anything in DPTR, DPH or DPL ?

Does the delay work or does it not exist ? Are you tramping on a register by accident ? Use the power of the assembler to make your life easier ! Assign variable to registers in data or idata memory.

Steve