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555 timer triggered from a bit stream

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I am trying to construct a pulsing circuit using a 555 timer. I want to trigger it from a 51-bit stream. I am feeding the bit stream into a shift register with the idea of clocking it in serially and then feeding it into a load of latches. Which also needs clocking. There is a particular bit in the stream I want to use as my trigger, which at some point will have a transition, so it needs to be continually monitored by the timer. The timer needs to O/P 32 pulses when it is triggered. It also needs a manual trigger (form of a button) which does the same thing. The 32 pulses will then be fed into the register to ensure the bits are on the right pins. Then it needs one final pulse, just for the latches to clock all of the bits into the latch!

This is quite complex and I hope I have explained this adequatly enough for someone to give me some pointers.
 
Since you already need all the digital circuitry to serialize latch etc. you should just generate the 32 pulses with digital logic. A FPGA or CPLD would be perfect for this task. You can program in all your logic into a single part. Xilinx and Altera have free tools that you can get off their websites. Xilinx has cheap CPLD kits that you can get through their website. Avnet.com also has good dev kits. The programable logic has the advantage that you can reprogram them if you make a mistake or need to chage the functionality without any soldering.

Hope this helps
Brent
 
Do you mean that you clock the 51 bits into the Shift Register and then examine one bit? Or do you have to look for the bit as it is being clocked?

As for the 32 pulses, all you need is a 5 bit binary counter and some control logic.

I don't understand exactly what you are trying to do. Otherwise I could make some suggestions

Len
 
Well, im making a binary calendar which runs off a signal from the British Atomic Clock. This is made up of a 51 bit stream. I want to clock my circuit everytime the day bit changes (ie every 24 hours, using the bit's transision as the trigger). This bit is number 35 in the stream.

I'm feeding the stream into a 32 bit shift register. The bits I need from the signal's bit stream are bits 17 to 35. The thing I'm having problems with, is working out how to trigger the timer circuit, and how to configure the 555 itmers so that I get enough pulses to go right through the stream and clock bits 17-35 in the register. And then set off another pulse to clock the latches which come directly after the register.

Sorry it wasn't more clear in the first place, and I don't want to use any progammable logic! Any help would be much appreciated though.
 
I would use a counter rather than a timer. How do you know when the bit stream starts? Is it all zeros normally and then a one appears as the leading bit?

Or does it have a sync word?

Once the start is detected, you simply have to start the counter, count the clock cycles and simultaneously clock the SR. When 35 bits are stored (since you said you want to use bits 17 to 35) in the SR, stop the counting and shifting and examine the relevant bit.

You have to have a clock anyway, so why use a timer?
 
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