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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If you use more than one of these ICs together with their outputs tied to the same input, you’ll need to manage the CS pins in order to ensure that both ICs don’t try to deliver data at the same time.
I have 15 output buttons and 4 digital inputs.
74LS673 (Big) 16-bit serial-in serial-out shift register
Yes, I finally have a reason to xatasheet the “diagonal diode” symbol in CircuitLab. Note that I’m assuming that the inputs rise to a positive voltage if not grounded; i.

There are also purpose built chips that scan the buttons connected as an array like the 74C Since it’s only 15 switches, another way this can be done is to use a shift register rather than an array.
With all of these you would need to handle debounce in code. Pressing SW4 pulls down IN2. The Data Available will return high to indicate acceptance of the new key after a normal debounce period.
Available output returns to a low level when the entered key is released – even if another is depressed. The logic diagram on the bottom of page 4 shows why: The most direct way to do it is to build a diode matrix: Load from the switches into the shift register 74l673 16 switches attached to 16 pullups, then step feed the word back to the micro. 74ls763 having 16 buttons using that method would be pushing that technique a tad.
Sign up or log in Sign up using Google. 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 and latch.
You even get to be able to detect SW0 thanks to the Data Available signal!

Pull-ups are required, may be internal to micro or not. Pressing SW1 pulls down IN0 only. You can use a couple of 74LS encoders as shown in their data sheet. Add pullup resistors if necessary. Anyone want to make some money via online consulting? A simple solution is to connect a diode from each input to every switch that should pull that input low.
clock, data and latch on the 74LS
I think I like the latter best since you can grab the complete switch status at one moment in time. This two-key roll-over is provided between any two switches. I’m assuming the inputs are dataseet pulled high by some means. You need to define what is to happen when 1 a second key is pressed while the first is held down 2 when the second key is released before the first and 3 74ls6733 the second key is released after the first.
In that case you would need datadheet form of keypad scanner. It sounds as though you need a proper keyboard matrix controller.
Perhaps a fritzing diagram and a simple sketch lighting 16 LEDs? As in the picture: You won’t be able to use your common ground switch arrangement but all other potential problems will be solved.
SN74LSN, BG-ELECTRONICS SN74LSN, SN74LS, 74LSN, 74LS
Internal debounce with single external capacitor. FYI, The most useful functions: I’ve searched the 74s673 and it doesn’t look like anyone has asked this yet.
There’s no asynchronous load function, like the load function on the 74LS This is an area where a datashwet excels – scanning a keyboard matrix in your case 4×4. The clock is CLK, pin 2 on the through-hole package shown at the top of page 2 in the datasheet. Furthermore, a scanned switch matrix is easy to de-bounce.
