Universal Shift Register 74LS194

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Tommy volts
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Universal Shift Register 74LS194

Post by Tommy volts » Mon Nov 29, 2004 8:22 am

I am building a pushbutton input 4 bit serial-in parallel-out shift register. I can use Four D flip-flops with synchronous clock pulse using a 0.3 hz clock(50% duty cycle 555 timer w/ LED on output already built).<p>Holding the push button down as the timer blinks from on to off (negative edge triggering) will load a "1" into the register. Leaving the the push button alone as the timer blinks from on to off will load a "0" into the register. In this manner, after 4 cycles of the clock, the user can manually load any 4 bit binary number into the register and the parallel output will light 4 LEDs which will show and store the binary number.<p>
To save alot of wiring around a Quad D-flip flop, I bought a 4 bit bidirectional Universal Shift Register.<p>the problem is that it appears from the 74194 data sheet that the minimum allowable clock speed for the chip is 25MHZ. Obviously way too fast for what I need. <p>Question 1: Is the minimum functional speed really 25MHZ? why so fast? <p>Question 2: is there any way that I can use the 74194 to accomplish what I am trying to do(i.e. manually input 4 bits)?<p>thank you.

Ron H
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Re: Universal Shift Register 74LS194

Post by Ron H » Mon Nov 29, 2004 10:29 am

The 74194 maximum clock frequency is a minimum of 25MHz (read the datasheet again). It will run at any arbitrarily low frequency. You should be able to use it to accomplish what you want.

Tommy volts
Posts: 149
Joined: Tue Oct 29, 2002 1:01 am
Location: Arizona
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Re: Universal Shift Register 74LS194

Post by Tommy volts » Mon Nov 29, 2004 11:39 am

Ron, <p>I believe you. <p>Thank you for your quick response.

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