Hello Mr. Frank Jin,

I don't see a RETI (return from interrupt) in your interrupt service routine (ISR). I see a RET (return) which is not the same thing.

It also seems you timer 0 ISR is to complicated. Why not just take care of resetting TL0 (timer zero low register) and TH0 (timer zero high register), set a flag and exit with a RETI.

Take care of business in a loop piece of software after your INIT (initialization) software.

Just my two cents worth of observations.

Regards,

Charles Bannister