C6670 1ms clock

henlee

Intellectual 840 points

Other Parts Discussed in Thread: SYSBIOS

I am trying to configure a 1ms system clock for:

- TMDSEVM6670LE,

- XDS560V2 mezzanine

- CCS6.0

- Sysbios 6_33_06_50

The example below runs for 60s if the clock period is set up correctly at 1ms. In the .cfg file provided with the original example, a clock is defined with Tick Period (us)=1000, and no timer is defined. Using these settings, the clock is updated every 8ms instead of 1ms measured by the time it takes the example to run to completion. If I change the clock Tick Period(us) to 122 instead of 1000, the clock is updated approximately every 1ms, and the example runs for 60s as it should.

// Simplified example from bios_6_33_06_50\packages\ti\sysbios\examples\generic\clock\clock.

Void main()
{
Clock_Handle clk1;
Clock_Params clkParams;

    Clock_Params_init(&clkParams);
    clkParams.period = 0;
    clkParams.startFlag = FALSE;
    clk1 = Clock_create(clk1Fxn, 60000, &clkParams, NULL);

Clock_start(clk1);

BIOS_start();

}

Void clk1Fxn(UArg arg0)

{

UInt32 time;

time = Clock_getTicks();

System_printf("System time in clk1Fxn = %lu\n", (ULong)time);

System_printf("Calling BIOS_exit() from clk1Fxn\n");

BIOS_exit(0);

}

I haven't found an explanation of how a timer is connected to a clock in SysBios references. I'm especially interested in eventually setting up the 1ms clock in startup code without using a .gel file.

Questions:

How does changing Tick Period(us) from 1000 to 122 in the example produce a clock period of 1ms?
Which timer does SysBios use as the default if a timer isn't specified?
Where is this default timer configured in SysBios?
If SysBios uses the timer configuration in evmc6670l.gel, where does it read these values?

over 11 years ago

0 Emmanuel Trinidad - Alicea over 11 years ago

TI__Genius 10260 points

Hi Henlee,

Documentation for the Clock module can be found here.

henlee said:

How does changing Tick Period(us) from 1000 to 122 in the example produce a clock period of 1ms?

The Clock_tickPeriod specifies how many microsecond for each Clock tick. If you want to set a clock period to 1ms, you need to set it in the clockParams.period field to the appropriate number of clock ticks.

    Clock_Handle clk1; 
    Clock_Params clkParams;

    Clock_Params_init(&clkParams);
    
    // assuming Clock_tickPeriod = 1000 microseconds. 
    clkParams.period = 1;                        // Clock will timeout every 1 tick.
    ...

The default for the Clock module is to operate in one-shot mode. If you want the Clock to timeout every 1ms you will need to set the Clock module to periodic mode in your .cfg file:

var Clock = xdc.useModule('ti.sysbios.knl.Clock');

// Tell the Clock module to use TickMode_PERIODIC
Clock.tickMode = Clock.TickMode_PERIODIC;

henlee said:

Which timer does SysBios use as the default if a timer isn't specified?

By default, SYS/BIOS is set to use any timer not already used by your code. Warning, this has changed in later releases. You can manually assign one in the .cfg file with:

Clock.timerId = 2;

henlee said:

Where is this default timer configured in SysBios?

The clock module configures the timer. You need only to use the clock module.

henlee said:

If SysBios uses the timer configuration in evmc6670l.gel, where does it read these values?

Either a bootloader or a gel file must be used to enable the clocks. SYS/BIOS requires these peripherals to be enabled before running.

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C6670 1ms clock