74HC Datasheet, 74HC stage Binary Counter Datasheet, buy 74HC, 74HC pdf, ic 74HC description/ordering information. The ‘HC devices are stage asynchronous binary counters, with the outputs of all stages available externally. A high. Data sheet acquired from Harris Semiconductor. SCHSD. Features. • Fully Static Operation. • Buffered Inputs. • Common Reset. • Negative.

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The 74VHC is another candidate – it has twin 4-bit counters in a package, so three ICs would be necessary. Dtasheet row address can be updated from the horizontal sync. Maybe a fast external counter for the lowest 4 or 8 bits, and the PIC generates the upper ones?

74HC4040 Datasheet PDF

Now, I need 5 ICs to make the counter – if it’s even fast enough. How about the 74HC? I’ll have to give that one some thought. This also ignores the fact that two 74HCs need to be chained to 7h4c4040 the bit address: The dot clock is I have to go take them out of my shopping cart now: Synchronous counters use extra logic to form the next state from the previous one directly, without waiting for clocks to ripple through, so the outputs settle faster.

In the schematic above, the ‘ counters increment the address on the rising edge of the clock, while the ‘ d-flop captures the data from the last address before it changes. Sign up Already a member?

I spent the afternoon re-working my ugly SOIC adapter board designs to reduce the ground-connection impedance and add on-board bypass caps.


I haven’t used VHC logic before, but keep seeing it around. Don’t forget that ground-bounce! If I were making more than a one-off project, I think the 25 MHz idea might be the way to go. Yeah, I had read about keeping video blanked outside adtasheet the active area.

Let’s run the numbers, dataxheet a 15pF load: Those bounces won’t kill this project. If I were going to build a bunch of these, I’d try harder to get the 74HC to work. They’re not completely general anymore, since now they assume standard corner pin supply connections, but they should be better for signal integrity.

Yes, delete it Cancel. Synchronization is an issue, but it’s worth thinking about – maybe if the PIC runs from the external I started with the VHC part this time: About Us Contact Hackaday.

I’m already bummed about the color thing I have a tube of 50 MHz cans around here that I could divide down, but since I have to order parts for this thing anyway, I might as well pick up the exact frequency for a few bucks.

VHC to the rescue? I’m going to ignore those timing calculations for the moment next log because there’s an even bigger problem here – it takes too long for the address to settle. I saw the 25 MHz trick in your terminal project – good to know. I’m using typical values for the moment; if it doesn’t work there, it’s not going to work worst-case, either.

Did I miss something on the ripple counters? Here’s a simplified schematic of the guts of the VGA framebuffer it ignores the reset and connections between the two ”s required to generate 19 bits of address.


So, what the heck, I’ll look at timing before slapping something together.

Musta been a bunch of pixie-dust in there, or a poor memory of 18 years ago. In this case, it’s not dtaasheet but registers. Next step – the rest of the logic and timing calculations. Maybe I’m doing this wrong? Doesn’t datasheet promising – although the typical 21ns 6V or 25ns 4. I think either one would definitely work, and it would make an interesting project, but I’ve somehow got it into my head that I need actual x It’s a shame, because the ‘ packs bits into a single package.

74HC Datasheet(PDF) – NXP Semiconductors

Cycling back the hsync for a second 74hf4040 is interesting. Monitors can handle some clock frequency variations. Surely the 74VHCwith its Mhz typical max clock frequency will do the job! Since it’s a ripple counter, Q0 flips, then Q1, then Q2, etc, so we have to add all the delays so see how long it takes for the address to settle to the next value. I can hook one to the four-channel scope and have a look at the delays between the LSB 74hx4040 successive bits.

I need 5 of them, which sucks.

Interesting discovery upon looking back