IC 74LS154 ??

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IC 74LS154 ??

Postby asan » Tue Feb 15, 2011 6:25 am

i use pic.. and only got 6 output port left. but i need 14 output.... can i use IC 74LS154 to get all the remaining output that i want??? help :(
asan
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Re: IC 74LS154 ??

Postby ABSF » Tue Feb 15, 2011 8:00 am

No you cant. 74154 is a 4-16 address decoder so only one output is selected each time. And further more it doesnt latch the output. Once the input disappears (deselected), so as the output. You can try it out with 16 LED and you'll find out that you cant keep an LED on and start doing other tasks. You cannot switch on more than one LED too.

There are many ways to expand the output ports. You can use a transparent Latch like 74HC373 or HC573, 74HC595 serial to parallel shift registers or I2C port expander like MAX7300 here:

http://www.maxim-ic.com/datasheet/index.mvp/id/3376

Actually the cheapest & easiest way is to get a fatter PIC.

Allen
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Re: IC 74LS154 ??

Postby Brian Griffin » Tue Feb 15, 2011 10:16 am

asan WROTE:i use pic.. and only got 6 output port left. but i need 14 output.... can i use IC 74LS154 to get all the remaining output that i want??? help :(


use a shift register like 74hc595. Gives you another 8 outputs. however if you want more, stack them togehter with another 74hc595. :)
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Re: IC 74LS154 ??

Postby ober » Tue Feb 15, 2011 10:58 am

ABSF WROTE:Actually the cheapest & easiest way is to get a fatter PIC.


I like the description of "fatter", can I a modify a bit? "Fatter & Taller"?

Yes, using 74HC595, that is serial to parallel shifter, very good IC. You can also use flip-flop or latch as recommended by Allen. Do share the result with us here.
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Re: IC 74LS154 ??

Postby asan » Tue Feb 15, 2011 5:14 pm

sori for not enough information i giv u. i only need one output selected in each time... n dont care if its latch or not.... because went the output from pic already gone i want the other 16 output also gone........ sory for misunderstanding.....
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