74LS688 DATASHEET PDF
Texas Instruments 74LS Logic Comparators are available at Mouser Electronics. Mouser offers inventory, pricing, & datasheets for Texas Instruments . December INTEGRATED CIRCUITS. 74HC/HCT 8-bit magnitude comparator. For a complete data sheet, please also download. Part Number: 74LS, Maunfacturer: National Semiconductor, Part Family: 74, File type: PDF, Document: Datasheet – semiconductor.
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You could then use it as a clock.
(Datasheet) 74LS pdf – SN74LS (1-page)
For example, going from 9 to A might give a false datasjeet of B for a few nanoseconds. It is a glitchy signal.
If you expect to use it, you need to turn the enable off during the time when the compare inputs are in transition.
Hi No it won’t. I got lost reading that. You can’t use it while the inputs are changing. As the address lines transition and settle out, they might very 74ls6888 set up a glitch that agrees with the test condition, well before you intended.
You’re depending too ddatasheet on the propagation delay of the 74 and the creating a clock pulse of the minimum required width t wclk on your datasheet. This is all fine. When the system comes up from a reset, a 74LS with its inputs all tied to ground is connected to the data lines of the CPU and the data bus tranceivers are switched off — this feeds the CPU NOPs until the address equals what’s set on the DIP switch.
Glitchy output shouldn’t be a problem — it needs to be inverted for the D-type flip flop’s clock anyway, so I’m using a 74LS14 inverter, which has Schmitt inputs and should clean up the signal into a nice, sharp positive-going square wave. Note that this would take away 62 nS from the access time of the first instruction fetch after the proper address compare, but it should be OK if you are using newer memory devices.
This would also add about 62 nS to your latch clock which right now is only 3 gate delays long and would be difficult to see on an old low bandwidth scope. I’ve never had to use one. It might work, but I don’t like it much.
Glitchy output shouldn’t be a problem — glitch, I see how you got your nickname. I’m not talking about little tiny noise spikes. This sets the D-type flip flop, which switches off the NOP datashete and turns on the bus tranceivers.
This might cause a false trigger if your address trap was at B. Here’s the pieces relevant to Power on Jump: There may be better ways to do this job so keep tinkering.
74LS datasheet,datasheets manu Page:5====[未知厂家] pdf datenblatt – –
A way to avoid that would be daasheet de-glitch the circuit by adding a synchronizing flip-flop running at 16MHz just before the latching flip-flop. It may even make it worse. It’s an 8-bit comparator, but it’s cheaper than the 74LS85 and has an enable input.
It’s comparing the high four address bits to a 4-position DIP switch. My calculations say yes, with lots of time to spare, but I’d like others’ opinions. Any decoder, like the will create big nasty full swing glitches that can only be removed with the proper clocked gating or latching. Hi I doubt you’ll be able to run the output of the directly to a clock. Just to scratch my own curious itch, what does the connect to? In other words, what function does it serve?
Comparator 74LS688 DIP20
I’m currently designing the power-on-jump circuit for my processor board. I don’t do well with word descriptions of circuits–can you draw a schematic? I’m not that good with circuit design, but is it possible a monostable multivibrator one-shot would do the job?