dco frequency range

The DCO frequency varies from chip to chip in the range shown in that table. If you want to know that in a particular chip, you need to measure it.

the above table is for single chip msp430g2553. But, I didn't get why there is so much of variation in single range itself. especially 16MHz to 26MHz.

The way DCO in MSP430G2553 is designed and manufactured makes it hard to produce the same frequency.

GURU MOORTHY said:

the above table is for single chip msp430g2553.

You won’t believe it, but I do too have a G2553, so there are at least two of them, each one with different frequencies somewhere between the specified min and max values. :)

GURU MOORTHY said:

 I didn't get why there is so much of variation in single range itself.

The DCO is an R/C oscillator. RSEL switches between resistors and DCOx between capacitors. While capacitors can be done quite precisely on silicon, depending only on structure geometry, resistors can’t be done that easily. Resulting in a wide variation for any R/C combination.
The 1x family (with even larger variation) did have an external R input, so you could add an exact resistor and get quite close DCO frequencies across different MSPs.

GURU MOORTHY,

To get the exact frequency, you can use a reference oscillator to dial in a pretty accurate Hz.  You can use DriverLib for that.  For example on my F5335 controller, I use the following code:

    PMM_setVCore(PMMCOREV_3);         // 20 Mhz

    UCS_clockSignalInit(
                UCS_FLLREF,
                UCS_XT1CLK_SELECT,
                UCS_CLOCK_DIVIDER_1);
    // Set ACLK = REFO
    UCS_clockSignalInit(
                UCS_ACLK,
                UCS_XT1CLK_SELECT,
                UCS_CLOCK_DIVIDER_1);
    UCS_initFLLSettle(  // 20 Mhz
            20000,
            610);

That code "scales' my low frequency crystal to dial in pretty accurate timing.

thank you...

The G2553 does have factory tested values stored in SegA
Yes they actually run a test on every single chip as to see what values to use as to get
1MHz,4MHz,8MHz and 16MHz DCO and stores them for you to use later,

But as temp and voltage affects RC oscillator and you're probably are not operating
at exact TI factory's temp and voltages, you will still be off by around +-1%