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In need of 1-4 bit parallel register which saves values under no power

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Dec 2, 2010
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i am using flip flop in a circuit to flip values on each clock cycle, i need replacement for flip flop with the ic having behaviour of flip flop but resets its output to last operating values after disconnecting and reconnecting power supply, or any 4 bit parallel register to add next to flip flop to retain its values. any help will be appreciated.


There may be some concept along the lines of flash memory, or bubble memory, or ferrite core memory, that you could put to use.

A slower method would be to charge a capacitor or supercapacitor or battery. Of course it would need to change state quickly in order to match whatever value is coming down the line, moment to moment. To change the state of these devices quickly requires power.

Depending on how fast your flip-flops are clocked, the cheapest solution may be a small microcontroller with built in EEPROM. You could do the flip-flop function in software and data retention would be 20 years or more!


clock speed is very slow, and mcu is not an option, solution needs to be smallest as possible
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You wont find a smaller solution than an MCU. If you use a 'real' flip-flop and memory you would have to create timing signals to write and read the memory and of course have a memory device as well. A sub $1 14-pin MCU can do this in one component.

ok, i'm now considering MCU, can u please recommend the smallest and best mcu for this operation.

There are many types, my personal preference is the PIC family from Microchip.
I dd a quick search on their web site and the cheapest MCU that can do what you want is the 16F526 which has 12 pins you can freely use as the inputs, outputs and the flip-flop clock. It also has 64 bytes of non-volatile memory to remember the flip-flop state and it's volume price is US$0.55. The only extra component it needs is a capacitor across it's supply lines but you would need that with a discrete IC design as well.

I checked the one-off price where I am in the UK and it was 0.85 which is about US$1.00


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