MSP430i20xx DCO calibration data

The calibrated frequency is 16.384MHz (2^14). Which frequency do you want to run the device with?

You can easily divide the frequency for MCLK and/or SMCLK by writing:

CSCTL0  =  0;                 // Internal Resistor
CSCTL1 |=  DIVM__2 | DIVS__4; // MCLK = DCO/2, SMCLK = DCO/4

This will give you MCLK = 8.192MHz and SMCLK = 4.096MHz - you can use other dividers, of course.

Setting the clock like

BCSCTL1 = CALBC1_1MHZ; // Set DCO range
DCOCTL  = CALDCO_1MHZ; // Set DCO step and modulation

is not applicable like in the F20xx devices.

Dennis

Dennis-san

Thank you for your "amazing quick" response!


I want 1-8MHz to reduce current consumption.

So,it is not acceptable MCLK/SMCLK divided DCO clock.

Do you have any idea that DCO operates 1-8MHz to reduce Icc.

best regards,

kyt

The device is designed to run it's DCO at 16.384MHz, even with the external resistor. You can feed in an external clock in bypass mode which can be in the range from 0 to 16.384MHz, but this might consume more power than the internal DCO which only draws 85µA @ 16.384MHz. And the SD24 needs the 16.384MHz clock for best performance. The significant power consumption is caused by the CPU:

So to save power you should use the clock dividers for MCLK and SMCLK while using the internal DCO running at 16.384MHz (or with a 20k precision external resistor). Dividers are 1, 2, 4, 8 and 16.

Dennis