Shift Register 8-Bit - SN74HC595 (COM-13699)

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1

This is a placeholder topic for “Shift Register 8-Bit - SN74HC595” comments.

The SN74HC595N is a simple 8-bit shift register IC. Simply put, this shift register is a device that allows additional inputs or outputs to be added to a microcontroller by converting data between parallel and serial formats. Your chosen microprocessor is able to communicate with the The SN74HC595N using serial information then gathers or outputs information in a parallel (multi-pin) format. Essentially it takes 8 bits from the serial input and then outputs them to 8 pins.

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2

If I have two components feeding data into the serial pin, is an OR gate required?

i.e. I’d like serial (pin 14 of the 595) to go high if either A or B are HIGH (where A and B are components like momentary push buttons).

| A | B | Ser |
|---|---|-----|
| 0 | 0 | 0   |
| 1 | 0 | 1   |
| 0 | 1 | 1   |
| 1 | 1 | 1   |

My instinct is that I will need an OR gate between A&B and the Serial pin.
However… maybe I can use diodes? As in, a diode from A to serial and a diode from B to serial.
Perhaps instead some kind of opt-isolator between A&B and the serial pin?

Any thoughts or experience appreciated :slight_smile:
Pix :heavy_heart_exclamation:

3

Hi Pix
Used to be called “Diode ORing”. Don’t know what it is called in these enlightened days.
Cheers Bob
Be aware of the diode forward voltage drop though.

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4

Thanks Bob.

Diode O-ring was the google search term I needed.

Thanks so much :slight_smile:

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