May 9, 2020 0 Comments

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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Interesting discovery upon looking back Now, I need 5 ICs to make the counter – if it’s even fast enough.

If I’m reading the datasheet correctly, the maximum delay from clock edge to valid outputs is datasheft I can hook one to the four-channel scope and have a look at the delays between the LSB and successive bits. It’s a shame, because the ‘ packs bits into a single package.

Synchronization is vatasheet issue, but it’s worth thinking about – maybe if the PIC runs from the external Let’s run the numbers, using a 15pF load: Synchronous counters use extra logic to form the next state from the previous one directly, without waiting for clocks datasheef ripple through, so the outputs settle faster.

The row address can be updated from the horizontal sync. This would work – with the 12ns SRAM access time, still way under the 40ns cycle time.

74HC4040 Datasheet PDF

I’m going to ignore those timing calculations for the moment next log because there’s an even 74hcc4040 problem here – it takes too long for the address to settle. They’re not completely general anymore, since now they assume standard corner pin supply connections, but they should be better for signal integrity. Here’s a simplified schematic of the guts of the VGA framebuffer it ignores the reset and connections eatasheet the two ”s required to generate 19 bits of address.

This could be interesting. I’m using typical values for the moment; if it doesn’t work there, it’s not going to work worst-case, either. For Qd the fourth bitthe typical tpd is given as 8. Next step – the rest of the logic and timing calculations. The dot clock is Yeah, I had read about keeping video blanked outside of the active area. I spent the 74hc400 re-working my ugly SOIC adapter board designs to reduce the ground-connection impedance and add on-board bypass caps.


I’ll have to give that 74hc040 some thought.

74HC Datasheet PDF –

So, with two of them connected to generate 19 bits of address, the tpd from the clock edge to the MSB settling is: Yes, delete it Cancel. Interestingly, it also has a synchronous clear, and connections for synchronous expansion between counters with lookahead carry outputs.

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.

In the store-each-dot-period-as-a-byte plan, this is trivial – I have full and easy control of all the singals on on a per-dot basis.

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. How about the 74HC? Sign up Already a member? I have to go take them out of my shopping cart now: The 74VHC is another candidate – it has twin 4-bit counters in a package, so three ICs would be necessary.

I need 5 of them, which sucks. Even if you could output a new address every cycle, that’s still only about half of the I started with the VHC part this time: Cycling back the hsync for a second counter is interesting.

I Hate Ripple Counters

The clock input on the ‘ works on the positive edge, so the schematic above changes a bit, but at least the addresses seem OK. If I were making more than a one-off project, I think datadheet 25 MHz idea might be the way to go.


If I were going to build a bunch of these, I’d try harder to get the 74HC to work. Surely the 74VHCwith its Mhz typical max clock frequency will do the job! Add in the 12 ns access time of the SRAM, and we’re definitely over budget. I’m already bummed about the color thing Synchronous Counters 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.

Maybe a fast external counter for the lowest 4 or 8 bits, and the PIC generates the upper ones? About Us Contact Hackaday. Did I miss something on the ripple counters? All these numbers involving multiples of propagation-delays are making me question even further how I got the ol’ LCD controller running.

Don’t forget that ground-bounce! So, what the heck, I’ll look at timing before slapping something together. In this case, it’s not memory but registers.

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 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 Doesn’t look promising – although the typical 21ns 6V or 25ns 4.

That should relax some timing as your MSB are no longer rely on the propagation from the lower bits. I haven’t used VHC logic before, but keep seeing it around. Musta been a bunch of pixie-dust in there, or a poor memory of 18 years ago.