delay between 2 events

[shoyur]

Maybe its a very simple question...

I need to know the time elapsed between 2 events,
3 inputs called : CK1, CK2, DATA

CK1-2 are for synchronizing (timing signals), DATA is a 16 bits serial data,
before I read data, there's a start signal, that is CK1+CK2 at high for 100uSec,
How to:
(pseudo)

[PCM programmer]

If you have some interface specification that you're trying to decode,
it's better if you tell us the name of the specification, and the manufacturer
and part number of the device. Code may already exist for it.
If there is a data sheet for the device, post a link to it.

Also post your PIC and CCS compiler version.

[shoyur]

version is PCWH 4.114
PIC16F877A

and its a digital radio tuner chip
Toshiba TC9147BP

http://www.datasheetcatalog.org/datasheets/2300/499314_DS.pdf

p.234-235 (not the pdf page but the printed page on image, its scanned pages pdf)

thank you

[PCM programmer]

You could read the data with an INT_EXT interrupt routine.
Let's say the PIC is running at 4 MHz. It takes about 30 instruction cycles
to get into the interrupt routine for a 16F-series PIC, if you only have one
interrupt routine. So at 4 MHz, this will take 30us.

On page 24 of the PDF link that you posted, it shows the detailed timing
of the incoming pulses. You could use the CK1 and DATA signals.
Connect CK1 to the External Interrupt pin. Set the interrupt to trigger on
the rising edge. The short CK1 pulses are only 20us long, and the Start
pulse is 100 us. It takes 30us just to get inside the int_ext isr, so you can
tell if you're in the Start pulse by just reading the CK1 line just after you
enter the isr. If you read a logic high level ('1'), then you've found the
Start pulse. You can set a static flag inside the isr to True, to indicate
to your isr code that you are "in progress" of clocking in a data word.
Or you could load a static byte variable with 17. Use this byte as a
"down counter" to indicate how many more interrupts must occur for
you to get all the data bits in the incoming word.

Then on the next interrupt, skip the next CK1 pulse. Then on the next 16
CK1 pulses (which means in the next 16 interrupts), read the DATA line
just after arriving in the isr, and left-shift the result into a global 'int16'
variable. Then set a global flag when it's finished, to tell the main code
that new data is available. Clear this flag when you start receiving a new
data word in the isr, so the main() routine won't try to read the global
'int16' value while it's being updated in the isr. Or, you could use a
circular buffer to store several sequential words, as you receive them
in the isr.

When you read the 16-bit global data word in main(), you will need to
disable interrupts temporarily. That's because you don't want to read the
data word and have the 2nd byte be changed by an interrupt while you
are reading the 1st byte in main().

I don't know the interval at which the Toshiba chip sends out a block of
data. Maybe the data sheet gives this information somewhere.

I don't want to do this project for you. I have given you an outline of
one possible way to do it. I don't want to do it for you.

[shoyur]

It sends data each time the user press a new command (+, -, fm, am, seek, etc.) so its not too fast.

Only using CK1 as reference for data is good idea.
The fact that 30uS is shorter than the start signal and longer than CK1 signals is excellent idea.
and removing interrupt while the 17+ bits enters is good too.

Thank you a lot. It answers well my problem.

[PCM programmer]

[shoyur]

Yes I didn't answer the right thing but understood what you meant (not removing interrupt but be sure it doesn't restart at beginning, considering its not a new start signal but just the continuous data per interrupt), yes I will come back in main and continue none stop.

thx again