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Issues on clockless uart

Started by Shashi April 21, 2004
Hi,
I'm doing a project in clockless uart..as u know that the primary
function of uart is parallel to serial conversion while transmitting
and serial to paralel conversion while receiving..I was wondering if
someone could tell me as how can i do a parallel to serial conversion
and vice versa without using a clock.

Note: This is a circuit whoch doesnt use a clock at all/ Asynchronous
Circuit/Clockless Circuit.

Thank You
SHASHI
Shashi wrote:

> Hi, > I'm doing a project in clockless uart..as u know that the primary > function of uart is parallel to serial conversion while transmitting > and serial to paralel conversion while receiving..I was wondering if > someone could tell me as how can i do a parallel to serial conversion > and vice versa without using a clock. > > Note: This is a circuit whoch doesnt use a clock at all/ Asynchronous > Circuit/Clockless Circuit. > > Thank You > SHASHI
you don.t use a clock for asynchronous data.
Do you mean without a baudrate clock?  If so, good luck.
Usually UARTs don't have a clock line used for communications,
since they are asynchronous, but they do use a clock internally
to generate the output data stream, or to sample the incoming
data.

Mike Anton

"Shashi" <shashi22k@rediffmail.com> wrote in message
news:7cdabebf.0404211144.38da229c@posting.google.com...
> Hi, > I'm doing a project in clockless uart..as u know that the primary > function of uart is parallel to serial conversion while transmitting > and serial to paralel conversion while receiving..I was wondering if > someone could tell me as how can i do a parallel to serial conversion > and vice versa without using a clock. > > Note: This is a circuit whoch doesnt use a clock at all/ Asynchronous > Circuit/Clockless Circuit. > > Thank You > SHASHI
Shashi wrote:
> Hi, > I'm doing a project in clockless uart..as u know that the primary > function of uart is parallel to serial conversion while transmitting > and serial to paralel conversion while receiving..I was wondering if > someone could tell me as how can i do a parallel to serial conversion > and vice versa without using a clock. > > Note: This is a circuit whoch doesnt use a clock at all/ Asynchronous > Circuit/Clockless Circuit.
You could do it with a string of one-shots, but I feel guilty just suggesting such a grotesque kludge. I just put my finger down my throat and now I feel much better.
> I was wondering if > > someone could tell me as how can i do a parallel to serial conversion > > and vice versa without using a clock. > > > > Note: This is a circuit whoch doesnt use a clock at all/ Asynchronous > > Circuit/Clockless Circuit. >
Use a tapped delay line. Inject a pulse to start, then time everything downstream off the taps. Loop the pulse back as necessary to extend the delay.
"Shashi" <shashi22k@rediffmail.com> escribi&#2013265923; en el mensaje
news:7cdabebf.0404211144.38da229c@posting.google.com...
> Hi, > I'm doing a project in clockless uart..as u know that the primary > function of uart is parallel to serial conversion while transmitting > and serial to paralel conversion while receiving..I was wondering if > someone could tell me as how can i do a parallel to serial conversion > and vice versa without using a clock. > > Note: This is a circuit whoch doesnt use a clock at all/ Asynchronous > Circuit/Clockless Circuit. > > Thank You > SHASHI
and how are you planing to "sample" the input bits without a clock?, if you already figured out that part, then i guess you could use some sort of state machine ("clocked" or controled by the same circuit that sampled the bits) to deserialise those sampled bits. what kind of UART is it anyway?, and what kind of coding uses? does it use a selfclocking code scheme?
"Shashi" <shashi22k@rediffmail.com> wrote in message
news:7cdabebf.0404211144.38da229c@posting.google.com...
> Hi, > I'm doing a project in clockless uart..as u know that the primary > function of uart is parallel to serial conversion while transmitting > and serial to paralel conversion while receiving..I was wondering if > someone could tell me as how can i do a parallel to serial conversion > and vice versa without using a clock. > > Note: This is a circuit whoch doesnt use a clock at all/ Asynchronous > Circuit/Clockless Circuit. > > Thank You > SHASHI
As serial output is in the time domain, you must use a timer. If you really don't want to use a clock then take your circuit diagram, remove the word "clock" and replace it with the words "timer/counter". Peter --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.659 / Virus Database: 423 - Release Date: 15/04/04
"Shashi" <shashi22k@rediffmail.com> wrote in message
news:7cdabebf.0404211144.38da229c@posting.google.com...
> Hi, > I'm doing a project in clockless uart..as u know that the primary > function of uart is parallel to serial conversion while transmitting > and serial to paralel conversion while receiving..I was wondering if > someone could tell me as how can i do a parallel to serial conversion > and vice versa without using a clock. > > Note: This is a circuit whoch doesnt use a clock at all/ Asynchronous > Circuit/Clockless Circuit. > > Thank You > SHASHI
If you're not trying to do an RS232 standard UART, you could use another standard that includes the clock in the data stream. There many other standards that allow you to derive the clock from the data stream. Or, did you mean an auto-bauding UART? Where the UART can derive the baud rate based on the assumption that it is receiving the characters "AT"? --Anthony
In comp.arch.embedded, Jim Stewart <jstewart@jkmicro.com> wrote:

>Shashi wrote: >> Hi, >> I'm doing a project in clockless uart..as u know that the primary >> function of uart is parallel to serial conversion while transmitting >> and serial to paralel conversion while receiving..I was wondering if >> someone could tell me as how can i do a parallel to serial conversion >> and vice versa without using a clock. >> >> Note: This is a circuit whoch doesnt use a clock at all/ Asynchronous >> Circuit/Clockless Circuit. > >You could do it with a string of one-shots, but >I feel guilty just suggesting such a grotesque >kludge.
I thought of that too, it seems like an interesting if a bit bizarre design exercise, but I didn't mention it because the post smells too much like a homework/class assignment.
>I just put my finger down my throat and now I >feel much better.
Ben Bradley wrote:
> In comp.arch.embedded, Jim Stewart <jstewart@jkmicro.com> wrote: > > >>Shashi wrote: >> >>>Hi, >>>I'm doing a project in clockless uart..as u know that the primary >>>function of uart is parallel to serial conversion while transmitting >>>and serial to paralel conversion while receiving..I was wondering if >>>someone could tell me as how can i do a parallel to serial conversion >>>and vice versa without using a clock. >>> >>>Note: This is a circuit whoch doesnt use a clock at all/ Asynchronous >>>Circuit/Clockless Circuit. >> >>You could do it with a string of one-shots, but >>I feel guilty just suggesting such a grotesque >>kludge. > > > I thought of that too, it seems like an interesting if a bit > bizarre design exercise, but I didn't mention it because the post > smells too much like a homework/class assignment.
I know. It is sad because the first computer I *really* understood was the PDP 8/l, which was a totally asyncronous design. Ironically, the only clock in the machine was for the tty "uart". If the machine broke in such a way as to stop the propagation of pulses, you had no way to scope anything. One of the tricks was to jumper the uart clock to the start key so you could poke around and find out where the pulse was getting lost.