DS1075

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the function of the registers are described. The register settings are nonvolatile, the values being stored

automatically in EEPROM when the registers are programmed.

Note: The register bits cannot be used to make mode or frequency changes on the fly. Changes can only

be made by powering the device up in “Programming” mode. For them to be become effective the device

must then be powered down and powered up again in “Operation” mode.

For programming purposes the register bits are divided into two 9-bit words, the “MUX” word

determines mode of operation and prescaler values. The “DIV” word sets the value of the programmable

divider.

MUX WORD Figure 2

(MSB)

(LSB)

0*

0*

0*

EN0

PDN

M

MSEL

DIV1

* These bits must be set to zero

This bit selects either the internal oscillator or the external/ crystal reference.

1=External/Crystal

0=Internal Oscillator

however, if the PDN bit is set to zero the E/I bit will be overridden by the logic level on the

PDN

Table 1

PDN

BIT

E/ I

PDN

PIN

OSCILLATOR

MODE

0

X

0

EXTERNAL/CRYSTAL

0

X

1

INTERNAL

1

X

0

POWER-DOWN

1

0

1

INTERNAL

1

1

1

EXTERNAL/CRYSTAL

DIV1

This bit allows the master clock to be routed directly to the output (DIV1=1). The N programmable

INTCLK or EXTCLK depending on which reference has been selected. If the Internal clock is selected

=INTOSC (which also equals MCLK and INTCLK). If DIV1=0 the prescaler and programmable divider

function normally.

MSEL

MSEL

=0 will switch in the prescaler (unless overridden by DIV1=1), with a divide-by number

determined by the M bit.

M

This bit sets the divide-by number for the prescaler. M=0 results in divide-by-4, M=1 results in divide-