SUMMARY: Hardware Flow Control on 4/470 serial ports

From: Joe Hartley (
Date: Tue Sep 22 1992 - 08:47:23 CDT

Well, I've gotten a number of responses to my request for info on hardware
flow control on my 4/470's serial ports. Here's a summary:
Jim Prescott {rit,tropix,ur-valhalla}!moscom!jgp

Suns cannot do bi-directional hardware flow control. If you enable the
"crtscts" stty flag the sun will stop output when CTS goes low on the
modem. While receiving a Sun will drop characters if it cannot keep
up; it will never lower RTS.

Brett Lymn

You need to use the stty option crtscts to enable the hardware handshaking.


Unix Consultant
SC Consultants Ltd.

Try ttysoftcar -n ttyb
Ken-ichi Sakaeda (
PFU Limited, Tokyo Japan.

I have SPARCstation-2 running on SunOS4.1.2.
Hardware flow control can toggle by ttysoftcar command.

I don't know you can use ttycoftcar on Sun-4/470.


The end result? It works to a point, but file transfers choke on me, due,
I believe to the inability of the port to handle the hardware handshaking
properly. Well, it's off to see if my Co-ALM board does any better.

Joe Hartley          |  -  Whenever you find that you are on the
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