ST 27C256B - CMOS or TTL ?

[netdudeuk]

Hi

I'm looking for some 32KB EPROMS for an NMOS 6502 project and have looked at the data sheet ( http://www.thierry-lequeu.fr/data/27C256.pdf ) for the ST 27C256B EPROM.

However, there is talk about both TTL and CMOS levels.  So, the question is, will these work ok with my NMOS 6502 and other TTL (buffer) chips, etc ?

Thanks

[amyk]

Look at page 5 - Vil, Vih, Vol, and Voh. The reason they mention both CMOS and TTL for Voh is because TTL usually needs more current sourced from its output than CMOS.

[netdudeuk]

Thanks Amy.

So, referring to the same V values here https://learn.sparkfun.com/tutorials/logic-levels/ttl-logic-levels it looks like I'm good to go.  Right ?

[free_electron]

Look at page 5 - Vil, Vih, Vol, and Voh. The reason they mention both CMOS and TTL for Voh is because TTL usually needs more current sourced from its output than CMOS.

TTL does not take any current in for a HIGH level... it DELIVERS current for a low level.
This is a common misconception.

the input if a true TTL gate is the emitter of a transistor. if you apply a logic '1' no current goes in. if you pull it low you send the transistor in conduction.
that is why you need to go as low as 2.4 volts anything above that does not turn the transistor on

[netdudeuk]

So I'm good to go ?

[amyk]

Look at page 5 - Vil, Vih, Vol, and Voh. The reason they mention both CMOS and TTL for Voh is because TTL usually needs more current sourced from its output than CMOS.

TTL does not take any current in for a HIGH level... it DELIVERS current for a low level.
This is a common misconception.

the input if a true TTL gate is the emitter of a transistor. if you apply a logic '1' no current goes in. if you pull it low you send the transistor in conduction.
that is why you need to go as low as 2.4 volts anything above that does not turn the transistor on

The transistor is leakier than the gate of a MOSFET.

[SeanB]

All that means is that the drive out is enough to either drive a CMOS input to well within it's switching levels, ie over 80% and below 20% or over 4V and below 1V, under all conditions. It can also drive TTL to it's levels of over 2.4V high and below 0.8V low as well.

Basically it will recognise any input voltage over 2.4V as high and below 1V as low. Outputs will drive to at least 4V with the rated load and will pull down to 0.8V with the rated load. Your typical TTL terminator is a 330R resistor to 5V and a 220R to ground, with the common point being the bus. Funny thing with the DIP and SIL terminators with plain resistors is they still work if put in backwards, just the floating voltage is wrong. This may not be noticed for a long time or may only give a very occasional random error.