Re: Sun Console Access

From: Dave Uhring (daveuhring_at_yahoo.com)
Date: 04/29/05 

Date: Fri, 29 Apr 2005 09:23:50 -0500

On Fri, 29 Apr 2005 11:31:30 +0200, Stefan Jankowski wrote:

>>>>>> Dave Uhring <daveuhring@yahoo.com> writes:
>
>> The Ultra 1 serial ports are labeled TTY-A and TTY-B but Sun
>> violated common practice for DTE ports by making them DB-25S
>> connectors rather than DB-25P.
>
> Is this really so? I was under the impression that since the serial
> ports (or at least port A) are mainly meant for plugging terminals
> into, they are actually configured as DCE-ends.

The Ultra 1 was designed as a workstation. TTY-A logically then would be
used to connect to a modem (DCE) instead. Although a DCE connector is
used it is wired as DTE. Hence the requirement for a null modem to
connect to a terminal or terminal emulating PeeCee or other workstation.

> (I never checked the
> specs though, and may be mistaken; incidentially however, on Ultra-5
> and 10 Models (which are otherwise mainly PeeCees with SPARC CPUs)
> port A ist still DB-25S while B is a DE-9P, and the logical conclusion
> seems to be that one is configured as DCE-end for OBP-access and the
> other as DTE to be compatible with the rest of the PeeCee-world...)

No. Both ports are DTE. The DB-25S port may be used for both
asynchronous and synchronous connections but it is DTE. If that were
wired as DCE no null modem would be required to connect to another Sun
machine, yet the null modem is required.

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