4 ms·
Have a look at http://www.visual6502.org/JSSim/ http://www.visual6502.org/JSSim/ That aside, I'm still wondering what you are on about. The "internal logic" of
by pixelfarmer 3y ago
Have a look at http://www.visual6502.org/JSSim/ http://www.visual6502.org/JSSim/
That aside, I'm still wondering what you are on about. The "internal logic" of something like a 7400 is fully defined by the transistors, so to understand that, you have to understand how transistors work. Luckily, we are not dealing with analogue computers, but digital/binary ones, so things can be simplified to on/off. Transistors are something like switchable resistors, ideally between zero resistance ("on") and infinite one ("off"). This state is controlled by the "base" (BJT) or "gate" (FET). Which means if this base/gate has a defined state, the output will have a defined state, and that is where the specifics of the respective 74XX chip are important -> chip manual will give all the required details. But as such there is no "start-up procedure" or anything with these things as long as they have no internal state, and NAND gates don't have that. Once we talk about flip-flops, latches, registers, and similar things, then we have state, and usually also some way to reset that state. 8 bit CPUs all come with a reset line for some reason, or handle this automatically as part of their power-up.
And that is where these "we build stuff from 74XX chips to a 8 bit CPU" video series come in, because they show all the CPU components, their wiring, and potentially also give access to a full schematic so you can follow the traces and see + understand what happens as part of the power-up.
- MichaelZuo 3y agoThanks for posting the link, that's pretty cool, but it leads to my question of how do you know they are correct approximations? > That aside, I'm still wondering what you are on about. The "internal logic" of something like a 7400 is fully defined by the transistors, so to understand that, you have to understand how transistors work. What I'm on about is precisely that the 'internal logic' of the 7400 is unknown and not fully defined. You make an assumption here, that does not seem to be backed up by any published source, "it's fully defined by the transistors". For example, it might very well be reliant on other aspects, such as the length of the circuit traces to function correctly.
- pixelfarmer 3y agohttps://www.ti.com/product/SN74LS00 https://www.ti.com/product/SN74LS00 Datasheet for a 7400 type chip (or actually multiple). Go check it out.
- MichaelZuo 3y agoYou linked to a completely different product, it says on the site "SN74LS00", "4-ch, 2-input, 4.75-V to 5.25-V bipolar NAND gates". Are you getting confused as to what a bipolar NAND gate is vs. what we were discussing (the SN7400 TTL chip)?
- pixelfarmer 3y agohttps://www.ti.com/product/SN7400 https://www.ti.com/product/SN7400 is also "4-ch, 2-input, 4.75-V to 5.25-V bipolar NAND gates". I mentioned BJT and FET, for the latter there is https://www.ti.com/product/SN74AHCT00 https://www.ti.com/product/SN74AHCT00 Might be useful to know what BJT and FET means and then you will see that standard / original TTL is always "bipolar", for example.
- MichaelZuo 3y agoDo you not realize that the design that TI currently sells is different from the 1965 design that we were discussing? They are even manufactured using very different technology. Like I said, just because it shares the same part number and is labelled "bipolar NAND gate" does not mean that it's approximately the same.
- pixelfarmer 3y agoWell, this obviously has nothing to do with boot-up of a CPU anymore, either, so I'm out now.