Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise . 74ls,, 74ls Matched Datasheet Manufacture, PDF . 1, 74ls, BIT SHIFT REGISTERS, Texas Instruments, 74ls pdf. Texas Instruments 74LS Logic – Shift Registers parts available at DigiKey. SN74LSDW Datasheet · SN74LSDW – Texas Instruments ·

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The MM74C key encoder. I have to do this without one button influencing the other. I’ve just acquired two 74LSs and need help understanding the datasheet. Pressing SW1 pulls down IN0 only. I have 15 output buttons and 4 digital inputs.

Pressing SW2 pulls down IN1 only. How to make a button activate its corresponding binary address Ask Question. Furthermore, a scanned switch matrix is easy to de-bounce. Serial in parallel out 74LS Another alternative is to turn your buttons into a rudimentary digital to analog convertor and feed that analog value into whatever analog to digital convertor you may have available.


There’s no single pin that performs a “latch” function. To change any data in the shift register at all, the clock must have a falling edge.

Post as a guest Name. Pressing SW4 pulls down IN2. That is an entirely different proposition. This is an area where a microcontroller excels – scanning a keyboard matrix in your datadheet 4×4. Email Required, but never shown. The clock is CLK, pin 2 on the through-hole package shown at the top of page dstasheet in the datasheet. There are other ways that use many diodes.

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Yes, my inputs are already pull-up, the problem is that with this type of configuration I can only recognize one key at a time, if I activate keys 1 and 2 at the same time the input dataheet receive 3. Parallel in serial out 74LS Let me try this Feed one output low through the shift register and read back the status on the common line.

Sign up using Facebook. The most direct way to do ratasheet is to build a diode matrix: Such an arrangement is called a “diode matrix”. Internal debounce with single external capacitor. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

However your statement “have to do this without one button influencing the datashet and comments dataheet you need the ability to detect more than one button pressed at the same time. Load from the switches into the shift register all 16 switches attached to 16 pullups, then step feed the word back to the micro.

Note that I’m assuming that the inputs rise to a positive voltage if not grounded; i. The output pins are pretty obvious, and I can GUESS at the clock, data and latch pins, but would totally appreciate if someone more knowledgeable could tell me which are the clock, data datqsheet latch. He just wants to “send a ground” to the input signals. I’ll take it from there. That’s what diodes are for.


74LS673 (Big) 16-bit serial-in serial-out shift register

With all of these you would need to handle debounce in code. Available output returns to a low level when the entered key is released – even if another is depressed. P1 through P15 are inputs for parallel-loading the shift register. There are also purpose built chips that scan the buttons connected as an array like the 74C Or if you have the ability to program one, a small ROM or FPGA can do it. The logic diagram on the bottom of page 4 shows why: You need to modify your question to clarify that you want to prevent two button datazheet simultaneously giving an erroneous code.

By clicking “Post Your Answer”, you acknowledge that you have read our updated terms dahasheet serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies.

Though having 16 buttons using that method would be pushing that technique a tad. I’ve searched the forums and it doesn’t look like anyone has asked this yet.