8051 serial problems

Tauno Voipio <tauno.voipio@iki.fi.NOSPAM.invalid> wrote in message news:<lFxhc.354$wN1.230@read3.inet.fi>...
> 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.

No wonder computers never work!

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

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

"Edo Reshef" <edoreshef@hotmail.com> wrote in message
news:7a494870.0404220047.647b3f63@posting.google.com...
> Tauno Voipio <tauno.voipio@iki.fi.NOSPAM.invalid> wrote in message
news:<lFxhc.354$wN1.230@read3.inet.fi>...
> > 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.
>
> No wonder computers never work!
>
> > Which crystal and what divisor are you using on the 8051's?
>
> 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

That seems correct.

Can you verify the transmission rate with an oscilloscope
(17.36 us / bit)?

Also, please check the signal edges on the RS-232 lines.

Tauno Voipio
tauno voipio @ iki fi

edoreshef@hotmail.com (Edo Reshef) wrote in message news:<7a494870.0404220047.647b3f63@posting.google.com>...
> Tauno Voipio <tauno.voipio@iki.fi.NOSPAM.invalid> wrote in message news:<lFxhc.354$wN1.230@read3.inet.fi>...
> > 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.
> 
> No wonder computers never work!
> 
> > Which crystal and what divisor are you using on the 8051's?
> 
> I'm using 11.0592Mhz

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

> dingoatemydonut@aol.com (Dingo) wrote:
> 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.

Edwin

"Edo Reshef" <edoreshef@hotmail.com> wrote in message
news:7a494870.0404221405.237cb752@posting.google.com...
> > dingoatemydonut@aol.com (Dingo) wrote:
> > 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!

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!


"Edwin Bland" <edwinb@socal.rr.com> wrote in message news:<PDclc.8896$nn3.3100@twister.socal.rr.com>...
> 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.
> 
> Edwin
> 
> "Edo Reshef" <edoreshef@hotmail.com> wrote in message
> news:7a494870.0404221405.237cb752@posting.google.com...
> > > dingoatemydonut@aol.com (Dingo) wrote:
> > > 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!