Port counter speed

[cicga]

Hi all,

Little help needed.

I am trying to use port counter.
In XMOS example count += 3. but in my tests code stop working if number less then 8 is used. Can somebody explain why?
Here is code:

#include<platform.h>

on stdcore[1]: out port toggle = XS1_PORT_1A;

int count;


void gen()
{

toggle <: 0 @ count ; // timestamped output

do {
{
count += 10;
toggle@count <: 1; // timed output
count += 10;
toggle@count <: 0; // timed output
}
} while (1);
}

int main()
{

par
{
on stdcore[1]:gen();
}

}

I am using XDE 12.2 and XC-1A

thanks
cicga

[lilltroll]

You need to have time to perform the instructions as well.

Take a look at the instructions used (using debug and or disassembly)

from
toggle <: 0 @ count ;

to
toggle@count <: 1; // timed output

their is maybe 5-7 instructions ?

If you miss the time on the port you will need to wait until the counter has wrapped around.

If you decrease the frequency of the counter for an example 1:256, it probably will work.

On the other-hand, if you need to create a signal with a frequency >> 1 MHz consider to use serialized 1-bit port instead.

Code: Select all

//init code with a 32 bit buffered port
while(1)
 toggle<:0b10101010101010101010101010101010;

[cicga]

Hi lilltroll,

unfortunatly sounds right:(

what i need is fine adjustment of pulse width depends on external conditions. Pulse width should be from 50ns up to 100 ns. and serialization cannot be fine adjusted because of clock devision settings is very rough.

thanks
cicga

[Bianco]

Did you build the code in release mode (-O2)?

[cicga]

lilltroll,

you kind of right that from

"
toggle <: 0 @ count ;

to
toggle@count <: 1; // timed output

their is maybe 5-7 instructions ?"

but inside loop the is no any instructons between

count+=5;
toggle@count <: 1

so how here can be delay?


bianco:

yes I build the code release mode(default settings). I am not sure about -O2 level. I doam not sure how to check it under 12.2.0 releaseXDE


thanks
cicga