RTL Logic

From: Randy McLaughlin <randy_at_s100-manuals.com>
Date: Fri Jan 7 22:54:42 2005

The specific circuits in question are a mix of TTL & RTL and are simple
gates easily substituted with all TTL.


----- Original Message -----
From: "Tony Duell" <ard_at_p850ug1.demon.co.uk>
To: <cctalk_at_classiccmp.org>
Sent: Friday, January 07, 2005 5:55 PM
Subject: Re: RTL Logic

>> OK, this might sound like a stupid question, but being somewhat ignorant
>> of
>> RTL logic in comparison to TTL and other designs, what, if anything, can
>> be
>> substituted for RTL logic chips?
>> For example, if I wanted to build one of Don's devices and I wasn't
>> concerned with using "vintage" chips, could I do it "plug-and-play" using
>> current TTL?
> It is difficult to mix RTL and TTL in the same circuit, the supply
> voltage and logic levels are different.
> RTL chips are slower, and have different switching characteristics to
> TTL. If the devices are used as plain digital devices, and if the timing
> delays are not critical, then you should be able to built one of those
> circuits using entirley TTL devices. But if they use gates as oscillators
> or monostables (read : If there are RC networks about), then you will
> almost certainly need to make some changes.
> The other thing to watch out for is that many older logic families
> (certainly DTL, I suspect RTL too) had passive (resistive) pull-ups on the
> outputs, and could be wire-ANDed without problems. TTL, of course cannot,
> unless you use open-collector devices with an external pull-up resistor.
> The bottom line : You can almost certainly make a functionally-identical
> device with TTL and the changes will not be that major, but there could
> well be changes, It may not be just a matter of replacing a NAND gate
> with a NAND gate, etc.
> -tony
Received on Fri Jan 07 2005 - 22:54:42 GMT

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