These parallel-in or serial-in, serial-out shift registers fea- ture gated clock inputs and an overriding clear input. All inputs are buffered to lower the drive. 74LS Counter Shift Registers are available at Mouser Electronics. Mouser offers inventory, pricing, & datasheets for 74LS Counter Shift Registers. Part Number: 74LS, Maunfacturer: Motorola, Part Family: 74, File type: PDF, Document: Datasheet – semiconductor.

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Capacitor Expert By Day, Enginerd 74s166 night. That is to reset it you need to put it low. This is the way most chips work.

74LS165N, 74LS165PC, 74LS166

I had one mysteriously in my box-o-bits Now my order of 74HC chips has arrived I have found that the pinouts are not only different but have different names. We didn’t get time to make the swap back then but the project is back on the table now and we’re both stumped as to why it’s not working. Therefore to take it out of reset you place it high. For those that follow, the correct pinouts are When high, this input enables the serial data input and couples the eight flip-flops for serial shifting with each clock pulse.

I did have all this working nicely with a chip: I started this thread whilst trying to get my head around the different pin labeling on the Serial data flow is inhibited during parallel loading. How long will receive a response.

I’ve stripped back my code to troubleshoot it. Don’t know where it came 74os166. What else in the data sheet are you having trouble with? Phillips or NXP as they are now can be a bit wordy but are easier to follow. Pin 6 is the clock inhibit and should be connected to ground for correct operation.


Maybe I’ve got the input pin pull-down resistors the wrong way round!? Your buying lead can then be posted, and the reliable suppliers will quote via our online message system or other channels soon.

At first I tried modifying the wiring then I stripped it all out and started over. The most misleading part of this image however is that the blue lead from Arduino GND looks like it goes to PIN 15 on the – it actually goes to the ground rail and PIN 15 is connected to Ard 8, but is hidden. Clocking is done on the low-to-high level edge of the clock pulse via a two input positive NOR gate, which permits one input to be used as a clock enable or clock inhibit function.

Does anyone have a keener eye than me? That’s exactly what I needed to know.

Want to post a buying lead? I have found that TI data sheets are always very thorougher but steeped in their own convention. Hence, I ran it all up with the and got on quite well with it. A change from low-to-high on the clock inhibit input should only be done when the clock input is high.

I hope this serves others too.

Motorola 74LS Series Datasheets. 74LS, SN54LS Datasheet.

No pin 13 is an output not an input. You will probably find a line over the words Master Reset. This will allow the system clock to be free running and the register stopped on command with the other clock input.


This indicates that the pin should have a zero to activate the name of the function. It should be connected to the input pin of the arduino or the serial input of a cascading chip. A buffered direct clear input overrides all other inputs, including the clock, and sets all flip-flops to zero. Clocking is inhibited when either of the clock inputs are held high, holding either input low enables the other clock input.

James’ datasheet link yields a somewhat friendlier datasheet than the one I’d found from TI. The was quite easy Datasjeet thought but the datasheet has gotten me a little foxed. My friend and I had both ordered some s but during the shipping wait I happily found a in my stash of bits.

74LS Datasheet(PDF) – TI store

By utilizing input clamping diodes, switching transients are minimized and system design simplified. Just out of curiosity Click here to Download. I don’t know if this helps The LS is a parallel-in or serial-in, serial-out shift register and has a complexity of 77 equivalent gates with gated clock inputs and an overriding clear input.

The image in my diagram had come from the TI datasheet. The connections to the Arduino are: Synchronous loading occurs on the next clock pulse when this is low and the datsheet data inputs are enabled. This is what I have so far Yep, I’m getting that.