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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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’m using typical values for the moment; if it doesn’t work there, it’s not going to work worst-case, 74hv4040.

Monitors can handle some clock frequency variations. Did I miss something on the ripple counters? This would work – with the 12ns SRAM access time, still way under the 40ns cycle time. I can hook one to the four-channel scope and have a look at the delays between the LSB and successive bits.

Cycling back the hsync for a second counter is interesting. About Us Contact Hackaday. The 74VHC is another candidate – it has twin 4-bit counters in a package, so three ICs would be necessary. So, with two of them connected to generate 19 bits of address, the tpd from the clock edge to the MSB settling is: Surely the 74VHCwith its Mhz typical max clock frequency will do the job!

I’ll have to give that one some thought. 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 Hate Ripple Counters

VHC to the rescue? If I were making more than a one-off project, I think the 25 MHz idea might be the way to go. 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. Don’t 74hc44040 that ground-bounce! If I were going to build a bunch of these, I’d try datashet to get the 74HC to work. Doesn’t look promising – although the typical 21ns 6V or 25ns 4.


74HC4040 Datasheet

The dot clock is In the store-each-dot-period-as-a-byte plan, this is trivial – Dtasheet have full and easy control of all the singals on on a per-dot basis. Let’s run the numbers, using a 15pF load: 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.

All these numbers involving multiples of propagation-delays are making me question even further how I got the ol’ LCD controller running.

Synchronization is an issue, but it’s worth thinking about – maybe if the Datasjeet runs from the external The clock input on the ‘ works on the positive edge, so the schematic above changes a bit, but at least the addresses seem OK. I started with the VHC part this time: In this case, it’s not memory 74hc4004 registers.

That should relax some timing as your MSB are no longer rely on the propagation from the lower bits. Interestingly, it also has a synchronous clear, and connections for synchronous expansion between counters with lookahead carry outputs. Synchronous Counters Synchronous counters use extra logic to form 74hc40440 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. I haven’t used VHC logic before, but keep seeing it around.


Yeah, I had read about keeping video blanked outside of the active area. I’m already bummed about the color thing Now, I need 5 ICs to make the counter – if it’s even fast 74uc4040. I think either one would definitely work, datashet it would make an interesting project, but I’ve somehow got it into my head that I need actual x This also ignores the fact that two 74HCs need to be chained to generate the bit address: Sign up Already a member?

This could be interesting. 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.

How about the 74HC?

I need 5 of them, which sucks. 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.

74HC Datasheet(PDF) – NXP Semiconductors

For Qd the fourth bitthe typical tpd is given as 8. I saw the 25 MHz trick in your terminal project – good to know. Next step – the rest of the logic and timing calculations. So, what the heck, I’ll look at timing before slapping something together. Yes, delete it Cancel. Add in the 12 ns access time of the SRAM, and we’re definitely over budget. Interesting discovery upon looking back Musta been a bunch of pixie-dust in there, or a poor memory of 18 years ago. If I’m reading the datasheet correctly, the maximum delay from clock edge to valid outputs is It’s a shame, because the ‘ packs bits into a single package.

I have to go take them out of my shopping cart now: