Texas Instruments MSP430x1xx manual DCOCTL, DCO Control Register

Basic Clock Module Registers

DCOCTL, DCO Control Register

7 6 5 4

3 2 1 0

DCOx

MODx

rw−0 rw−1 rw−1 rw−0 rw−0 rw−0 rw−0 rw−0

DCOx	Bits	DCO frequency select. These bits select which of the eight discrete DCO
	7-5	frequencies of the RSELx setting is selected.
MODx	Bits	Modulator selection. These bits define how often the fDCO+1 frequency is
	4-0	used within a period of 32 DCOCLK cycles. During the remaining clock
		cycles (32−MOD) the f DCO frequency is used. Not useable when DCOx=7.

BCSCTL1, Basic Clock System Control Register 1

7 6 5 4

3 2 1 0

XT2OFF

XTS

DIVAx

XT5V

RSELx

rw−(1) rw−(0) rw−(0) rw−(0) rw−0 rw−1 rw−0 rw−0

XT2OFF	Bit 7	XT2 off. This bit turns off the XT2 oscillator
		0	XT2 is on
		1	XT2 is off if it is not used for MCLK or SMCLK.
XTS	Bit 6	LFXT1 mode select.
		0	Low frequency mode
		1	High frequency mode
DIVAx	Bits	Divider for ACLK
	5-4	00	/1
		01	/2
		10	/4
		11	/8
XT5V	Bit 3	Unused. XT5V should always be reset.
RSELx	Bits	Resistor Select. The internal resistor is selected in eight different steps.
	2-0	The value of the resistor defines the nominal frequency. The lowest
		nominal frequency is selected by setting RSELx=0.

Basic Clock Module 4-15