I just stumbled over a chip called SN74159 (http://www.bg-electronics.de/datenblaetter/Schaltkreise/SN74159.pdf).
A 4 to 16 line decoder with active LOW as well as open-collector outputs and two active LOW chip-select inputs.
According to the datasheet it has a average propagation delay of 24 to 36 ns.

The outputs are open-collector types, so they can easily connected together as wired-or, combining two or more "address ranges".
The same chip is available with totem-pole outputs as SN74154.

And lucky me I have an dealer for electronic components that is only a few kilometers away where I can pick up my orders without shipping costs.
So I couldn't resist to order some of this to play with.

Mario.

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How should I know what I think, until I hear what I've said.

In my opinion, that's not the holy grail of address decoding.
What you may not realize is that it's in a 24-pin DIP package.
24-pin DIP packages are .4 inches wide, so it occupies a large amount of board space.

The 74138/74145 are in a 16-pin/.2 inch wide package.
So they occupy significantly less board space, which is probably why they are very popular for address decoding.

Toshi

Keep in mind that the propagation delay is only valid for a <= 400 ohm pullup. So it requires at least 12.5 mA to keep it fast but 16 mA is already the maximum it can drive. Sounds like thin ice to me.

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6502 sources on GitHub: https://github.com/Klaus2m5

The "holy grail" was meant ironic. I saw that this chip is a pudgy one, but working on a breadboard or standard euro-pcb cards, this fact is not really important to me by now. I'm still in the phase of learning how things fit together and like a child I start playing with bigger building blocks.
Saving board space will be important much later I think. By now I play on a big breadboard with a W65C02S running "slowly" with a 1MHz can oscillator to reduce the risk of timing and noise or ringing problems with all the breadboard-wires. Currently my setup is even RAMless, only a 8k EEPROM is connected to the upper 8k running small programs.
Adressdecoding is done with a 74HC138 along wit a 74HC00 and a 74HC04 as "support" chips providing the possibility to combine and invert signals if needed. To this minimal setup I can connect several chips or devices to play with.
But, again "like a child", if I stumble over interesting things, suddenly thousands of ideas flying around my head how this thing can be used for. At this point it's really hard to resist to buy this thing, especially if the price is low and my wife is not around me (the last two facts are combined by NAND what means I have always a 3 of 4 chance to get the toy)

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How should I know what I think, until I hear what I've said.

All the 138's I have here, and all the 154's (24-pin) except my first ones that were TTL and LSTTL, are .3" wide. The 74154 and 74LS154 were .6" wide and I used them in a project about 1980. My NSC CMOS data book doesn't show an HC(T)159, which I guess makes sense. My old old (Feb '76) National TTL data book from Radio Shack doesn't show a '159 of any kind, so I can't check the width.

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Thanks for the correction on the package widths.

Toshi

An analog mux/de-mux can very easily be used as an open-collector decoder. One example is the 4067, a one-of-sixteen device originally issued as a 4000 series IC and now also available in 74HC and HCT versions. http://www.ti.com/lit/ds/symlink/cd74hc4067.pdf

To use a mux/de-mux as an active-low, open collector decoder, simply ground the Common i/o pin -- or use it as an active-low enable input.

(The same overall scheme can be applied to yield an active-high decoder. Just tie the Common i/o pin high instead. And replace all the pull-up resistors with pull-down resistors, of course.)

Obviously the power consumption of a 74HC/HCT device will be far less than that of a 74159. As for the package, it seems TI does not off a version in .3" DIP. Dunno 'bout other manufacturers, though...

-- Jeff

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In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

Just watch out for those delays of 50-80ns from select inputs to switch outputs.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Terribly slow logic, not to mention power-hungry and easily upset by noise.

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

Hmm... We are all in agreement about the speed of an 'HC4067, but to describe it as power-hungry, especially as compared to a 74159 (not even LS159), seems pretty crazy. Ditto for "easily upset by noise," as noise immunity is a well-established advantage of CMOS.

ETA: oops, it was the TTL logic you were deprecating? Maybe I mis-read your post. Garth posted a caveat about the 'HC4067, and it seemed you were doing the same.

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In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html

I was referring to the 74159. However, the 'HC4067 probably won't cause any nosebleeds due to its blistering speed.

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

Correct me if I am wrong, but in my opinion it has to do with the open drain outputs. They require a pullup resistor <= 400 Ohm to meat the maximum propagation delay criteria. This pullup resistor eats >= 12.5 mA on an active low output and a decoder has always 1 active output. It doesn't matter in this case, wether the technology used is TTL or CMOS. Same goes for noise immunity as the low to high transition is rather slow due to the passive high side and may cause an unexpected glitch at the receiver.

Because of these problems open drain outputs became less popular with CMOS technology and are only ment to retain backward compatiblity with existing circuits. No current design should use them especially when it comes to tight timing requirements.

P.S. Just read BDD's response: 4067 "blistering speed" adds on top of all open drain driver problems. Plus I don't know if a HC4067 can drive 12.5 mA to ground rail and if not would worsen the timing and the noise resilliance.

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6502 sources on GitHub: https://github.com/Klaus2m5

Darn-- I think you just finished it off. According to the data sheet at http://www.ti.com/lit/ds/symlink/cd74hc4067.pdf, its worst-case resistance at 6V, 25 deg C is 140 ohms, which is not low enough to pull down to a valid "0" against a 390-ohm pullup.

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?