8051 serial problems

This has a strong scent of a speed / distorsion error. It seems that after 6 bits, the 8051 is off by one bit time.

Please remember that initially the RS-232 standard limited the transfer speed to 20000 bits/s. There may be edge slow-down capacitors at either or both ends of the RS-232 data lines.

Which crystal and what divisor are you using on the 8051's?

Tauno Voipio tauno voipio @ iki fi

No wonder computers never work!

I'm using 11.0592Mhz And that the Init code: MOV PCON,#80h MOV SCON,#0C8H ;SET SERIAL PORT TO MODE 3 MOV TCON,#01H MOV TMOD,#21H ;SET TIMER 0 TO MODE 1 - 16 BIT MODE ;AND TIMER 1 TO MODE 2 - AUTO RELOAD MODE MOV TH1,#0FFH ;SET TIMER 1 TO PRODUCE 57600 BAUD (0FFH) ? SETB TR1 ;START TIMER 1

Are you sure your emulator isn't using an on-board 10Mhz crystal?

That's actually my main suspicion, I think the Ceibo DS-51 could have an Internal clock that runs at 12Mhz, DS-51 documentation says nothing about it. Anyway I will to physically look for crystal in the emulator in few dayz since it's weekend here... I'll keep you updated!

Hi,

My Ceibo emulator came with a default 24.0 Mhz crystal. It has divider jumpers... with the default being at 12.0 Mhz. I had to get another the crystal to get nonmultiple frequencies.

Edw> > Are you sure your emulator isn't using an on-board 10Mhz crystal?

Problem Solved! Ceibo manual doesn't say anything about it, but you can choose External OR Internal clocking inside the device. Thanks to everyone here I opened the emulator and found a crystal! I changed it and it works perfect. I changed 12.0mhz crystal with 11.0592mhz - exactly 10% difference! Nice one! I'm actually quite impressed from the skills people showed around, I guess I have lots to learn.

Really thanks guys, you helped a lot!