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’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.
Even if you could output a new address every cycle, that’s still only about half of the If I’m reading the datasheet correctly, the maximum delay from clock edge to valid outputs is I’ll have to give that one some thought.
The row address can be updated from the horizontal sync. Musta been a bunch of pixie-dust in there, or a poor memory of 18 years ago.
They’re not completely general anymore, since now they assume standard corner pin supply connections, but they should be better for signal integrity. Those bounces won’t kill this project.
74HC4040 Datasheet PDF
All these numbers involving multiples of propagation-delays are making me question even further how I got the ol’ LCD controller running. Interesting discovery upon looking back Yes, delete it Cancel. I can hook one to the four-channel scope and have a look at the delays between the LSB and successive bits. So, with two of them connected to generate 19 bits of address, the tpd from the clock edge to the MSB settling is: I started with 74hcc4040 VHC part this time: In this case, it’s not memory but registers.
How about the 74HC? For Qd the fourth bitthe typical tpd is given as 8. Doesn’t look promising – although the typical 21ns 6V or 25ns 4. Next step – the rest of the logic and timing calculations.
74HC data sheet datasheet & applicatoin notes – Datasheet Archive
I spent the afternoon re-working my ugly SOIC adapter board designs to reduce the ground-connection impedance and add on-board bypass caps.
VHC to the rescue? 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.
Now, I need 5 ICs to make the counter – if it’s even 74hcc4040 enough. I haven’t used VHC logic before, but keep seeing it around.
Synchronous counters dataheet extra logic to form the next state from the previous one directly, without waiting for clocks to ripple through, so the outputs settle faster. So, what the heck, I’ll look at timing before slapping something together. 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. Surely the 74VHCwith datashest Mhz typical max clock frequency will do the job!
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’m using typical values for the moment; if it doesn’t work there, it’s not going dataheet work worst-case, either.
That should relax some timing as your MSB are no longer rely on the propagation from the lower bits. 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.
74HC4040 Datasheet PDF
About Us Contact Hackaday. What about using the fastest PIC available and bitbanging the address lines? Sign up Already a member? If I were going to build a bunch of these, I’d try harder to get the 74HC to work.
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 74h4040 address.
I’m already bummed about the color thing I have to go take them out of my shopping cart now: Datasheey could be interesting. I saw the 25 MHz trick in your terminal project – good to know.
It’s a shame, because the ‘ packs bits into a single package. Did I miss something on the ripple counters? This also ignores the fact that two 74HCs need to be chained to generate the bit address: I need 5 of them, which sucks. Maybe a fast external counter for the lowest 4 or 8 bits, and the PIC generates the upper ones? If I were making more than a one-off project, I think the 25 MHz idea might be the way to go.
This would work – with the 12ns SRAM access time, still way under the 40ns cycle time.