Arduino Forum

Using Arduino => General Electronics => Topic started by: Zedkon on Mar 18, 2013, 07:02 pm

Title: 74HC574N, what's it good for?
Post by: Zedkon on Mar 18, 2013, 07:02 pm
I recently went for some component shopping and on my list I had some shift registers. Mind you, I'm new to integrated circuits and when NONE of the shops I visited had the 74HC595 I decided to just buy something with a similar name, hoping that it would work in a similar way. But the data sheets go on and on about it being an "Octal D-type flip-flop; positive edge-trigger; 3-state" and it working as a "Bus interface". Can I use this IC for any LED based projects? Or any beginner's projects for that matter?
Title: Re: 74HC574N, what's it good for?
Post by: Grumpy_Mike on Mar 18, 2013, 07:07 pm
Yes, connect it's data up to 8 output pins. Then connect another output pin to the clock.
You can then latch 8 LEDs from 9 pins.

However if you add another latch to the same output pins and clock it with a different pin you then get 16 LEDs from 10 pins.
For each additional latch you get 8 more LEDs for only one more output pin.
Any use to you?
Title: Re: 74HC574N, what's it good for?
Post by: mixania on Mar 18, 2013, 07:18 pm
Shift Registers are cool when you want to free some pins on your Arduino.
Title: Re: 74HC574N, what's it good for?
Post by: MarkT on Mar 19, 2013, 12:15 am
the 574 (in fact the '174, '274, '374 and possibly the '474 too) are clocked D-latches.  The typical use
for such a chip is in a microprocessor system to gate the system databus into an I/O device only when the
specific I/O address is decoded.

An address decoder is used to drive the clock (common to all the latches), the data bus is then copied to the output
of the latch only when the correct I/O address is present - you have written a value to the device!

For latches with tristate outputs they can be used to read from an I/O device - the OE (output enable)
pin is driven from the address decoder - however latching is not necessary for this, a '244 or '245 can
used (tri-state buffer).

Basically these chips are designed for parallel I/O, not serial I/O like the '595
Title: Re: 74HC574N, what's it good for?
Post by: Zedkon on Mar 19, 2013, 08:01 pm
Wow, quite fascinating, I'm sure these ICs will come in handy someday, if not, then I'll be sure to find a use for them at some point. Thanks for all the advice guys!