What''s a UART?
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Posts: 46,084
OK, I'll take it :-)
UART = Universal Asynchronous Receiver Transmitter
This is a "thing" (usually hardware but now days often software) that
converts asynchronous serial data to a form usable by a microprocessor. Your
PC has them. So do most microprocessors. The Stamp has them in software form
which as the gist of the other question (this is often called a "bit banged"
UART).
Asynchronous means there is no clock. Instead, a start bit marks the data
and then each bit has a predetermined time slice. Other systems use a bit
clock (my PAKs, for example) and that's synchronous. They do make USARTs
which do both.
Hope that helps.
Al Williams
AWC
*New: AWC Quarterly Industry Newsletter
http://www.al-williams.com/mailman/listinfo/embeddedtech
Original Message
From: Christopher Dundorf [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=5S1nW-8DJOnsQSUlktSyGzyL8DhU3IDxcUtd7nH3StMKn-gSa2J2gSgwKHz6ikFto_fnGVf27ZIJP7RI]cdundorf@j...[/url
Sent: Tuesday, February 03, 2004 7:42 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] What's a UART?
I've seen the term before many a time but specifically what is a UART and
how does it relate to serial coms on a Basic Stamp?
Thanks,
Chris
<<<>>>
Date: Tue, 03 Feb 2004 21:31:20 -0000
From: "suri_list" <suri_list@y...>
Subject: Re: OT : How does the stamp implement multiple UARTS on all pins
thanks this answer makes sense. I was suprised that the hw uart on
the pic was able to connect to all i/o.
its a software uart : thats why it can bit bang on all bits.
in our case we need to implement 6 serial connxns from the atmega128
which has 2 uarts. seems like the best we could do is run two serial
from them and the rest would have to be bit banged.
thanks
--- In basicstamps@yahoogroups.com, "Allan Lane" <allan.lane@h...>
wrote:
> The BasicStamp can do these things because it uses
> a "bit-bang" uart in software. When you issue
> SEROUT 16, 16384, [noparse][[/noparse]"Hi"],
> a software routine sends the bits out port '16'
> (the built-in serial port) and controls the
> timing of the serial bits with a timing loop.
>
> This is why you can only send out one port
> at a time -- but you can send out any port.
>
> The PIC has a hardware UART on-chip. To use
> a hardware UART, you simply write to the
> UART's transmit register, and it handles all
> bit timing in the background.
>
> The benefit of this is that your processor
> can be doing other stuff while the byte is
> being sent.
>
> If you had multiple hardware uarts, your
> Stamp would only have to talk to them when
> a byte was ready -- not have to sit there and
> ONLY send out bytes, or ONLY recieve bytes,
> and oh by the way the Stamp can't do both at
> the same time.
>
> It's the 'simultaneous' aspect which is
> desirable and people pay for.
>
> --- In basicstamps@yahoogroups.com, "suri_list" <suri_list@y...>
> wrote:
> > I have a question regarding using a MCU to implement multiple
> serial
> > (UART)
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UART = Universal Asynchronous Receiver Transmitter
This is a "thing" (usually hardware but now days often software) that
converts asynchronous serial data to a form usable by a microprocessor. Your
PC has them. So do most microprocessors. The Stamp has them in software form
which as the gist of the other question (this is often called a "bit banged"
UART).
Asynchronous means there is no clock. Instead, a start bit marks the data
and then each bit has a predetermined time slice. Other systems use a bit
clock (my PAKs, for example) and that's synchronous. They do make USARTs
which do both.
Hope that helps.
Al Williams
AWC
*New: AWC Quarterly Industry Newsletter
http://www.al-williams.com/mailman/listinfo/embeddedtech
Original Message
From: Christopher Dundorf [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=5S1nW-8DJOnsQSUlktSyGzyL8DhU3IDxcUtd7nH3StMKn-gSa2J2gSgwKHz6ikFto_fnGVf27ZIJP7RI]cdundorf@j...[/url
Sent: Tuesday, February 03, 2004 7:42 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] What's a UART?
I've seen the term before many a time but specifically what is a UART and
how does it relate to serial coms on a Basic Stamp?
Thanks,
Chris
<<<>>>
Date: Tue, 03 Feb 2004 21:31:20 -0000
From: "suri_list" <suri_list@y...>
Subject: Re: OT : How does the stamp implement multiple UARTS on all pins
thanks this answer makes sense. I was suprised that the hw uart on
the pic was able to connect to all i/o.
its a software uart : thats why it can bit bang on all bits.
in our case we need to implement 6 serial connxns from the atmega128
which has 2 uarts. seems like the best we could do is run two serial
from them and the rest would have to be bit banged.
thanks
--- In basicstamps@yahoogroups.com, "Allan Lane" <allan.lane@h...>
wrote:
> The BasicStamp can do these things because it uses
> a "bit-bang" uart in software. When you issue
> SEROUT 16, 16384, [noparse][[/noparse]"Hi"],
> a software routine sends the bits out port '16'
> (the built-in serial port) and controls the
> timing of the serial bits with a timing loop.
>
> This is why you can only send out one port
> at a time -- but you can send out any port.
>
> The PIC has a hardware UART on-chip. To use
> a hardware UART, you simply write to the
> UART's transmit register, and it handles all
> bit timing in the background.
>
> The benefit of this is that your processor
> can be doing other stuff while the byte is
> being sent.
>
> If you had multiple hardware uarts, your
> Stamp would only have to talk to them when
> a byte was ready -- not have to sit there and
> ONLY send out bytes, or ONLY recieve bytes,
> and oh by the way the Stamp can't do both at
> the same time.
>
> It's the 'simultaneous' aspect which is
> desirable and people pay for.
>
> --- In basicstamps@yahoogroups.com, "suri_list" <suri_list@y...>
> wrote:
> > I have a question regarding using a MCU to implement multiple
> serial
> > (UART)
________________________________________________________________
The best thing to hit the Internet in years - Juno SpeedBand!
Surf the Web up to FIVE TIMES FASTER!
Only $14.95/ month - visit www.juno.com to sign up today!
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
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To visit your group on the web, go to:
http://groups.yahoo.com/group/basicstamps/
To unsubscribe from this group, send an email to:
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Your use of Yahoo! Groups is subject to:
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