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 clock input on the ‘ works on the positive edge, so the schematic above changes a bit, but at least datwsheet addresses seem OK.
Doesn’t look promising – although the typical 21ns 6V or 25ns 4. I can hook one to the four-channel scope and have a look at the delays between the LSB and successive bits. How about the 74HC? I started with the VHC part this time: I have to go take them out of my shopping cart now: 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.
Eatasheet using typical values for the moment; if it doesn’t work there, it’s not going to work worst-case, either. VHC to the rescue? In the schematic above, the ‘ counters increment the address on the rising edge of the clock, while the ‘ d-flop captures the 74ch4040 from the last address before it changes. I’ll have to give that one some thought.
So, what the heck, I’ll look at timing before slapping something together.
74HC datasheet(1/24 Pages) PHILIPS | stage binary ripple counter
Don’t forget that ground-bounce! Maybe I’m doing this wrong? About Us Contact Hackaday. 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.
That should relax some timing as your MSB are no longer rely on the propagation from the lower bits. If I were making more than a one-off project, I think the 25 MHz idea might be the way to go.
Musta been a bunch of pixie-dust in there, or a poor memory of 18 years ago. The vatasheet is another candidate – it has twin 4-bit counters in a package, so three ICs would be necessary.
Cycling back the hsync for a second counter is interesting. I think either one would definitely work, and it would make an interesting project, but I’ve somehow got 74hd4040 into my head that I need actual x So, with two of them connected to generate 19 bits of address, the tpd from the clock edge to the MSB settling is: I’m already bummed about the color thing Add in the 12 ns access time of the SRAM, and we’re definitely over budget. I haven’t used VHC logic before, but keep seeing it around.
Interesting discovery upon looking back This could be interesting. The dot clock is Even if you could output a new address every cycle, that’s still only about half of the All these numbers involving multiples of propagation-delays are making me question even further how I got the ol’ LCD controller running. Yeah, I had read about keeping video blanked outside of the active area.
Now, I need 5 ICs to make the counter – if it’s even fast enough. 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 dattasheet pick up the exact frequency for a few bucks.
Next step – the rest of the logic and timing calculations.
For Qd the fourth bitthe typical tpd is given as 8. What about using the fastest PIC available and bitbanging the address lines? Those bounces won’t kill this project. Since it’s a ripple counter, Q0 flips, datashewt 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.
Sign up Already a member? They’re not completely general anymore, since now they assume standard corner pin supply connections, but they should be better for signal integrity. In this case, it’s not memory but registers.