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 Hate Ripple Counters | Details |

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. I’ll have to give that one some thought. Monitors can handle some clock frequency variations. For Qd the fourth bitthe typical tpd is given as 8. They’re not completely general anymore, since now they assume standard corner pin supply connections, but they should be better for signal integrity.

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

Don’t forget that ground-bounce! I started with the VHC part this time: All these numbers involving multiples of propagation-delays are making me question even further how I got the ol’ LCD controller running.

I need 5 of them, which sucks. That should relax some timing as your MSB are no longer rely on the propagation from the lower bits.


This could be interesting. I saw the 25 MHz trick in your terminal project – good to know.

74HC Datasheet PDF –

The dot clock is Doesn’t look promising – although the typical 21ns 6V or 25ns 4. Let’s run the numbers, using a 15pF load: About Us Contact Hackaday. 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’m going to ignore those timing calculations datssheet the moment next log because there’s an even bigger problem here – it takes too long for the address to settle. Sign up Already a member? Maybe I’m doing this wrong? How about the 74HC? 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 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 fatasheet.

If I’m reading the datasheet correctly, the maximum delay from clock edge to valid outputs is Now, I need 5 ICs to make the counter – if it’s even fast enough. This would work – with the 12ns SRAM access time, still way under the 40ns cycle time.

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. Next step – the rest of the logic and timing calculations. Interesting discovery upon looking back Did I miss something on the ripple counters? Yeah, I had read about keeping video blanked outside of the active area. What about using the fastest PIC available and bitbanging the address lines? Interestingly, it also has a synchronous clear, and connections for synchronous expansion between counters with lookahead carry outputs.


Yes, delete it Cancel. In this case, it’s not memory but registers. It’s a shame, because the ‘ packs bits into a single package. Maybe a fast external counter for the lowest 4 or 8 bits, and the PIC generates the upper ones? The row address can be updated from the horizontal sync.

74HC4040 Datasheet

I’m using typical values for the moment; if it doesn’t work there, it’s not going to work worst-case, either. If I were making 74h4c040 than a one-off project, I think the 25 MHz idea might be the way to go.

Those bounces won’t kill this project. I’m already bummed about the color thing The clock input on the ‘ works on the positive edge, so the schematic above changes a bit, but at least the addresses seem OK. So, with two of them connected to generate 19 bits of address, the tpd from the clock edge to the MSB settling is: Synchronization is an issue, but it’s worth thinking about – maybe if the PIC runs from the external Cycling back the hsync for a second counter is interesting.