JB <PICLIST@MITVMA.MIT.EDU> wrote:

> The frustrating part for me is that I still don't have a definitive
> reference for whether the start bit is 1.5t, 1t or 0.5t, and of what
> polarity relative to the stop bit.

    JB:

    It's 1t, and of opposite polarity relative to the stop bit.

> Is this supposed to be right for sending H'28' at 9600/n/8/1?
>
> 1       156uS <start bit
> 0       104uS <bit0
> 1       104uS
> 0       104uS
> 0       104uS
> 0       104uS
> 0       104uS
> 0       104uS
> 1       104uS <bit7
> 0       104uS <stop bit

    No, that's not right; it should look like this:

        1       104uS <start bit
        0       104uS <bit0
        0       104uS
        0       104uS
        1       104uS
        0       104uS
        1       104uS
        0       104uS
        0       104uS <bit7
        0       104+uS <stop bit

    Note that the start bit is 104 uS, I've moved the "1" bits around
    so you're actually sending 28 (your table would've sent 82), and
    the stop bit can be any length longer than 104 uS.  It's
    probably best to make your stop bit 208 uS or longer; that'll
    give your receiver a little more time to buffer the data and
    prepare to re-sync on the next start bit.

    Also... Before the very first start bit taht you send after
    power-up, your transmit line should be in the "stop" state,
    preferably for at least 1 bit-time (104 uS).

    -Andy


=== Andrew Warren - fastfwd@ix.netcom.com
=== Fast Forward Engineering - San Diego, California
=== http://www.geocities.com/SiliconValley/2499