Dear Andy Neil,

Thanks for your advices, I have gone to Keil website and then I found A251, L251, OH251.

But if I have MCS-251 hex file, how can I debug it (view it in assmbler code as I have done with MCS-51 in SIM51 or in TS Control) ?

Have you ever used MCS-251 ?, please share experience to me because I'm new. Thanks a lot.

Best Regards,
Minh Nhat