If you take a look at the output structure used with ECL, which was quite common
at one time for sync along with negative-going video on workstation type
monitors having very high bandwidth, you'll see the levels that ECL uses range
between -1.75 and -0.9, for 0 and 1, respectively. The supply voltages were
Vcc=0.0 Volts, and Vee= -5.2 Volts. Other involved voltages include a Vbb
at -1.29 Volts, and Vtt at -2 Volts.
The typical logic element consists of a diff-amp buffered with an emitter
follower. This is very fast, but doesn't swing very far. The emitter follower
can't sink current, so the termination is vital. The inputs to the logic
element are typically the base of an npn transistor.
If you want a good text on signal integrity, I'd recommend the Motorola MECL
System Design Handbook, by the way. It's considered by many to be THE
definitive work on signal integrity in high speed systems, though it's been
around for over 20 years, and, though we don't use ECL as much as was once the
practice, the signal integrity issues remain the same. Now that logic swing is
gradually approaching the range used with ECL, it seems the work presented is
becoming more rather than less relevant. The signal integrity analysis software
used by Mentor and by Cadence is based on the work presented in this document
and it's still available.
Dick
----- Original Message -----
From: "Bill Pechter" <pechter_at_bg-tc-ppp1580.monmouth.com>
To: <classiccmp_at_classiccmp.org>
Sent: Wednesday, May 09, 2001 7:23 AM
Subject: Re: Converting TTL monitor to Analog
> > "TTL" refers to Transistor/Transistor Logic. Low usually .5VDC to zero, high
>~4VDC, usually 5VDC.
> >
> > IIRC "ECL" is Emitter Coupled Logic. Don't remember the voltage levels.
> >
> > Bob Mason
>
> I think ECL had -3 volts as one of the levels... don't remember the rest
> but I thought it was +10 or +12v.
>
> Anyone here ever service a DEC KL10 and know?
>
> Bill
>
>
Received on Wed May 09 2001 - 09:23:55 BST