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Serial port question

C

CWatters

Jan 1, 1970
0
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?
 
M

Mjolinor

Jan 1, 1970
0
CWatters said:
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?

No, in my experiance it will work with all the other lines floating.
 
N

Norm Dresner

Jan 1, 1970
0
CWatters said:
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?

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
 
R

R. Steve Walz

Jan 1, 1970
0
CWatters said:
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?
------------
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
 
C

CWatters

Jan 1, 1970
0
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
 
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