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PIC16F877 interfacing with MM74HC595 for LED application.

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arup

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using tpic6b595n

Hello,

I have an application where i have to drive 8 leds thro' MM74HC595 using PIC16F877A.
Short Description of MM74HC595:
15,1....7 -> o/p pins where LEDs are connected.
11 -> SCK
12 -> RCK
13 -> /G
14 -> SER (Data line from Microcontroller)
10 -> /SCLR

I require following pins from micro to interface 595:
RB0 -> pin 13(/G) to select the chip.
RB1 -> pin 11(SCK) for clock.
RB3 -> pin 14(SER) for data o/p to 595

My question is :

a) are the above signals(just interfacing) enough(optimized) for the subjected application except VDD and GND.
b) Is there any requirement for RCK clock pin??
c) how should i connect /SCLR pin?

pls help.

regards,
arp
 

Re: PIC16F877 interfacing with MM74HC595 for LED application

arup,

Did you find an answer for this?

I am using a 16F688, interfaced to a TPIC6B595N

which is very similar to what your doing.

I dont have an answer for you at this point as I am unsure of it as well.

Hopefully someone with the right answer may post here.

Cheers
Aurbo
 

Re: PIC16F877 interfacing with MM74HC595 for LED application

a) are the above signals(just interfacing) enough(optimized) for the subjected application except VDD and GND.

- You need to drive RCLK (Register clock) pin as well to transfer content of shift register to output latch. You need rising edge to do that.

b) Is there any requirement for RCK clock pin??

-look under a

c) how should i connect /SCLR pin?

This is shift register clear function, not needed in most cases, just tie to +5V.


If you use MCU SPI, you don't have to use "bit banging" to drive shift register, SPI's hardware can do that for you. You just place byte in Tx register and let it rip. Although if you are having difficulties understanding '595 data sheet, using any off-beat paths in design might out of your scope.
 

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