Serial port question

C

CWatters

Guest
I've got a very simple application involving a PC transmitting (only) to a
display over RS232. In theory only two wires are required Tx and Gnd as the
display can "keep up" with whatever data rate the PC can produce. I'm using
a test program that has the following handshake options "None, XON/XOFF,
Hardware etc". I'm assuming that if I select "none" then the test program
won't use handshaking but what about the UART itself?

Does the UART in a PC need hardware handshake lines pulled to a particular
state in order to transmit?
 
"CWatters" <colin.watters@pandoraBOX.be> wrote in message
news:xO6Yb.3596$wl6.232498@phobos.telenet-ops.be...
I've got a very simple application involving a PC transmitting (only) to a
display over RS232. In theory only two wires are required Tx and Gnd as
the
display can "keep up" with whatever data rate the PC can produce. I'm
using
a test program that has the following handshake options "None, XON/XOFF,
Hardware etc". I'm assuming that if I select "none" then the test program
won't use handshaking but what about the UART itself?

Does the UART in a PC need hardware handshake lines pulled to a particular
state in order to transmit?
Click to expand...
No, in my experiance it will work with all the other lines floating.
 
"CWatters" <colin.watters@pandoraBOX.be> wrote in message
news:xO6Yb.3596$wl6.232498@phobos.telenet-ops.be...
I've got a very simple application involving a PC transmitting (only) to a
display over RS232. In theory only two wires are required Tx and Gnd as
the
display can "keep up" with whatever data rate the PC can produce. I'm
using
a test program that has the following handshake options "None, XON/XOFF,
Hardware etc". I'm assuming that if I select "none" then the test program
won't use handshaking but what about the UART itself?

Does the UART in a PC need hardware handshake lines pulled to a particular
state in order to transmit?
Click to expand...
The protocols (both hardware and software) that govern PC serial
communications are *all* dictated by the software. The UARTs themselves are
just reporters of electrical facts.

Norm
 
no it does not. but it may need the
DSR line pulled up ?. that is just a guess.


CWatters wrote:

I've got a very simple application involving a PC transmitting (only) to a
display over RS232. In theory only two wires are required Tx and Gnd as the
display can "keep up" with whatever data rate the PC can produce. I'm using
a test program that has the following handshake options "None, XON/XOFF,
Hardware etc". I'm assuming that if I select "none" then the test program
won't use handshaking but what about the UART itself?

Does the UART in a PC need hardware handshake lines pulled to a particular
state in order to transmit?
Click to expand...
 
CWatters wrote:
I've got a very simple application involving a PC transmitting (only) to a
display over RS232. In theory only two wires are required Tx and Gnd as the
display can "keep up" with whatever data rate the PC can produce. I'm using
a test program that has the following handshake options "None, XON/XOFF,
Hardware etc". I'm assuming that if I select "none" then the test program
won't use handshaking but what about the UART itself?

Does the UART in a PC need hardware handshake lines pulled to a particular
state in order to transmit?
------------
Click to expand...
If you bit-bang the port IO itself, no, but if you use the BIOS, then
yes, you'll need the DSR and CTS to be fooled because the BIOS will
require it.

-Steve
--
-Steve Walz rstevew@armory.com ftp://ftp.armory.com/pub/user/rstevew
Electronics Site!! 1000's of Files and Dirs!! With Schematics Galore!!
http://www.armory.com/~rstevew or http://www.armory.com/~rstevew/Public
 
Thanks for all the replies. I finally figured out that the display I was
driving needed a higher voltage power supply.

If anyone else needs a simple app to test a serial port device then I
recommend "Serial Device Tester" by Hack Consulting at
http://www.hackconsulting.com
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top