I followed the setup for the timer 0, but my ljmp command at 0Bh just never execute.

Is it becos i am using timer 2 and 1 at the same time ??

I am using timer 1 as serial port timer, and i need to use timer2 and timer 0 as baud rate generater. 2 and 1 are working fine but timer 0 just cannot work ?? why ?

0bH:
ljmp gen

main:
setb es
setb ea
mov tmod,21h
setb et0
mov th0,#0adh
mov tl0,#3dh
setb tr0
.
.
gen: push psw,dph,dpl,acc,b
mov c,p1.0
cpl c
mov p1.0,c
clr tf0
pop b,acc,dpl,dph,psw
reti
.
.
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your attention is appreaciated