I have a synchronous 4-bit up/down counter, and in the data sheet it stands that there are 4 pins where I can enter a 4 bit preset number, but it doesn't say what this number represents. I believe that it is the first number in the counting sequence (e.g. if preset is 0001, the counter will start from 0010), am I right?
Synchronous 4-Bit Up/Down Counters preset
binarycmoscounterdigital-logicttl
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Wow, your question isn't terribly focused, and it's not obvious what you are really asking for. But let me give this one a try. Sorry if I didn't get it quite right.
Ripple counter vs. normal synchronous counter: Who says that people don't use ripple counters? People use whatever they have available that works best. In FPGAs, nobody uses a ripple counter because the logic blocks do a sync counter so much better than a ripple. But if you're designing a custom chip then a ripple counter can be more advantageous when it comes to power consumption and logic size. It would not surprise me at all of some people use ripple counters in their ASICs. Sync counters would still be better for speed and simplicity of timing.
Gray Counter vs. Binary Counter: People do use gray counters in ASICs and custom chips. In FPGAs, where binary counters are faster, people still use Gray counters when the count value has to go across clock domains, such as in FIFOs.
Multi-phase clocks: These are certainly used in the design. There are reasons why the PLLs in FPGAs can often output 0, 90, 180, and 270 deg phase-shifted versions of the original clocks. But as the clock frequencies go up, using multiple clocks gets harder due to clock skew and clock distribution issues. It's not impossible at high frequencies but it just isn't done as much.
Sync vs. Async: Sync circuits are not just easier to simulate but easier to design and easier to guarantee that they work correctly. Verification and timing analysis tools are difficult-to-impossible to use with async circuits.
MCU Counter Circuit: Do you KNOW that there are no MCUs that do it that way? If it did, how could you tell? Maybe the prescalers on the timer are ripple counters. Maybe the timer itself is a Gray-coded counter and reading/writing the registers automatically converts it to/from binary. My point is this: the guys who design super-low power MCUs (like the MSP430) do every trick in the book to reduce power consumption. Many of those tricks, like using ripple counters and Gray code where appropriate, are completely invisible to people like you and I. They can, and probably are, using those tricks plus a couple of hundred other tricks that you haven't thought of yet.
One thing that you haven't mentioned is the use of completely async circuits. This is where all of your talk about clocks eventually goes when taken to it's logical conclusion. There have been companies that have tried to build large-scale CPUs that are completely async, including one group that tried to bring an async ARM to market. The benefits are amazing: super-low power, faster processing, and less EMI among them. But the disadvantages are more amazing yet. The main one is that the complexity of designing this chip is huge and is not economically viable today. A secondary problem is that the number of transistors about doubles when compared to an equivalent sync chip.
Even so, there are CPUs on the market today that use async logic in some of its blocks, like the FPU, but nobody uses it on a large scale.
In general, the usual answer to this sort of problem is to pipeline. You might consider adding pipeline registers immediately after the 10-bit comparators, before the logic that combines them into the enable signal for the next stage. To keep the resulting enable signal aligned with the correct data in the data path, you'll probably also need a pipeline register for the data, too.
But yes, you can also use the technique described in the other question. For your specific 10-bit counter example, instead of counting from 0 to 1003 and using a comparator to identify state 999 to turn off the enable signal, you could make it an 11-bit counter that counts from -1000 to 3. The MSB of this counter is your enable signal, and when the count gets to 3[1], you reload the counter with -1000 ... and also load an auxiliary 9-bit count-down counter with the value 249. Each time this auxiliary counter reaches -1 (MSB set) is the start of another subframe (in addition to the one that starts at the beginning of the main frame).
[1]Note that detecting "3" is a function of just 3 bits — the MSB and the two LSBs — not a function of 11 bits.
Best Answer
The 74HC192/3 have asynchronous load. As soon as** you assert the /LOAD input, the outputs will change to reflect the 4-bit input you have applied to the PRESET inputs, and the outputs stay there as long as /LOAD is low regardless of clock or anything else (except RESET which overrides the /LOAD).
When you remove the /LOAD (and RESET is not active) then the counter may count up or down from the preset number, if it receives a rising clock edge on one of the clock inputs.
** after some tens of nanoseconds with a 5V supply