SUMMARY: ALM-2 hardware flow control

From: David Way (
Date: Wed Apr 14 1993 - 17:31:32 CDT

Sun Managers,

On Friday, April 2, 1993, I wrote:

> I'm having trouble configuring some of the ports on an ALM-2 serial mux (on
> a 4/490, 4.1.1) to use RTS/CTS handshaking. Four of the ports (0-3) work
> fine, while 2 others (4 & 5) that I have modems connected to seem to ignore
> the handshake signals. I can find no way in which ports 0-3 are set up
> any differently than ports 4 & 5, likewise for the corresponding serial port
> on each modem. It doesn't seem to be the modem's fault at all - I can plug
> either of the modems on ports 4 & 5 into any of the ports 0-3, and there's
> no problem, which also suggests that the cables are ok. Also, with a
> breakout box, I have observed normal behavior of the CTS line from the
> modem on ports 0-3 (i.e. toggling up and down as the modem accepts bufferload
> of data), but not on ports 4 & 5 (CTS changes state once just after data
> starts flowing, then stays that way till the modem hangs).
> Grepping my list of SunOS patches for "ALM", I found the following:
> 1100137-01 ALM flow control patch
> 1100194-02 SunOS 4.1.1, 4.1: ALM2 flow control
> 2100225-02 SunOS 4.1, 4.1.1, 4.1_PSR_A :printers, terminals, plotters,
> hang on serial and ALM2 p
> Does anyone have any experience with any of these patches, especially in
> connection with the problem I've described above ? I can't find any of
> them on any of the anonymous-ftpable sun-fixes sites I know of - perhaps
> someone who has them could send it to me, or tell me where I can find
> them.

All 17 responders said the same thing - only the first 4 ports of an ALM-2
support hardware flow control, by design . Apparently this is an
`often'-asked question, so I won't bore the readership with a rehash of
something that has already been discussed. I will gladly email a copy of
all the responses I got to anyone to asks.

Many thanks to the following who responded: (Ron Russell) (Ron Stanonik)
 wallen@cogsci.UCSD.EDU (Mark R. Wallen)
 jsin@JANET.UCLA.EDU (John Sin) (Dr. Robert Pasken)
 lemmanp@ohsu.EDU (Paul Lemman) (Christopher Davis) (William F. Krauss III)
 stern@sunne.East.Sun.COM (Hal Stern - NE Area Systems Engineer) (Robert C. Bethel) (Matt Goheen) (Mike Jewison) (Ed Arnold)
 fireball! (Tom Poage)
 joef@VFL.Paramax.COM (Joseph M. Fedock) (John DiMarco) (Randy Diffenderfer)

David Way  McDonald Observatory/Astronomy Dept.- Univ. of Texas, Austin 
(office) RLM 16.206 (voice) 471-7439 (internet)

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