[SOLVED] a digital circuit without reset signal

[Josephchiang]

Does the digital circuit which without reset signal exist?

if it don't, it mean the "power on reset circuit" is needed in each digital circuit.

The difficulty to implement the power on reset circuit on my chip is that the reset time interval is a very long time (Max. about 1 second) as shown in the figure.



So it need a very large value of Resistor and Capacitor to achieve this goal.

But it is not practicable in the fully on chip design.


Any suggestion is helpful,

Thanks in advance.


Best regards,
Joseph

 

[barry]

There are certainly digital circuits that don't have a reset. However, they may initialize to an unknown state. This may or may not be a problem, depending on the specific application.

If you really need an on-chip reset, and can't accommodate a large RC (I don't know why), you could use a counter.

 

[Josephchiang]

There are certainly digital circuits that don't have a reset. However, they may initialize to an unknown state. This may or may not be a problem, depending on the specific application.

If you really need an on-chip reset, and can't accommodate a large RC (I don't know why), you could use a counter.

Thanks a lot,

Would you please elaborate the specific application. I have no idea about it.

Any reference or material is helpful.

Actually, The a large RC value may could be achieve on chip, but it is not economical due to cost lots of chip area.

The one square micro-meter approximate to 1 pF

The sheet resistance of poly resistor is about 30~1xx ohm

 

[ads-ee]

Use a very short power on reset to reset the counter based reset. Use google to find a counter reset circuit.

Regards

 

[Josephchiang]

Use a very short power on reset to reset the counter based reset. Use google to find a counter reset circuit.

Regards

I'm glad to see your reply again but I was still confused that what type of application don't have a reset. Could you give me more clue?

How to avoid going wrong when using the digital circuit without reset signal?

Have any precaution exist?

Thanks

 

[barry]

I'm glad to see your reply again but I was still confused that what type of application don't have a reset. Could you give me more clue?

How to avoid going wrong when using the digital circuit without reset signal?

Have any precaution exist?

Thanks

There millions of circuits that don't have a reset. The question is : Does your application require a reset? Does it require that you start from a specific state?
Just as a stupid example, suppose you have a circuit that blinks a light-on for 100 clock cycles, off for 100 cycles. You would use a counter for this application, but it wouldn't be necessary to have a reset-it could power up with an unknown state in the counter, but eventually would settle in to proper operation.

 

[Josephchiang]

It is really a good example.

Now, I know what your meaning.

Thanks a lot.