Need advice for creating nS time delay

[Darrel Taylor]

I guess it should be RTFCD. (current datasheet)

P.S. Hello skimask.

[Ioannis]

Hi skimask! Where have you been? Its been a long time...

Well about the pin capacitance, I don't think it is a good idea in respect of the difference between chips. The delay won't be standard. If precision is needed don't think about it.

Can you provide more info about your project Sayzer?

Ioannis

[sayzer]

Ioannis,

I am interfacing with PYD1998 (digital output pyrodetector) and the communication requires a pause min.200nS.

I am using 12F675 (intosc) and the min. delay is 1uS.

1uS does not give precise results.
Since, a delay faster then 1uS at 4Mhz is not possible, now I have no choice but use a chip with 8Mhz intosc ( based on Alain's calculation I can get 500nS).

This time, the unit cost will be on table.

...
Then was looking farther and came across this ...
Apparently, you can run a 16F628A at 4Ghz.
A 1ns delay would just be a NOP.

Anyone can show me a practical application of this?


P.S. - Welcome back Skimask! Howzit?

[Ioannis]

Although I have not made anything on FPGA's I see them now as an approrpiate solution.

They can be really fast!

Now about the device, I could not find a detailed pdf. Only a 2-page short datasheet. Do you have a complete copy? From the short one I think it is not as fast as you have stated.

Ioannis

[sayzer]

Although I have not made anything on FPGA's I see them now as an approrpiate solution.

They can be really fast!

Now about the device, I could not find a detailed pdf. Only a 2-page short datasheet. Do you have a complete copy? From the short one I think it is not as fast as you have stated.

Ioannis

Here are the detailed data sheets.

Unfortunately, application note file is 224KB, forum limit is 200KB.

[Acetronics2]

Hi, Sayzer

Hmmmm, 10 µm center bandpass ... that's a human motion detector !!!

Did you ask for the application Kit from Perkin-Elmer ???

http://optoelectronics.perkinelmer.c...pyroappkit.pdf


By the way ...

having a closer look to your datasheet ... it appears ( to me ... LOL )

1) you must wait for the sensor's output HIGH level ( PIC as input : Hi Z state ...)

2) When pic ready, generate a LOW 200ns MINIMUM pulse, then a HIGH 200 ns MINIMUM pulse

3) Pic as Input for 1µS MINIMUM ( Hi - Z ! ) then reads level


4) generate 200ns MINI low pulse , then 200 ns MINI high pulse ... etc, etc : we're back to step 2)

that repeated for the 15 bits ...

No "hyper high speed" processor required here as 200ns and 1µs are MINIMA ... ( the data is read at the speed given by the low to high transitions sent by the processor

so, try 24µs instead of 200ns and 24µS instead of 1µs waiting ... ( it's the pauseus minimum @ 4 Mhz ...)
after that you will be able to speed it up a bit using @nop !!!




Alain

[sayzer]

Hi, Sayzer

Hmmmm, 10 µm center bandpass ... that's a human motion detector !!!

Did you ask for the application Kit from Perkin-Elmer ???

http://optoelectronics.perkinelmer.c...pyroappkit.pdf

Alain

When I run the circuit on F877 with 20Mhz, I get very good results.
So I have no problem with the circuit; communication etc.