DS1065

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PIN DESCRIPTIONS

Input/Output Pin (IN/OUT): This pin is the main oscillator output, with a frequency determined by

clock reference, M and N dividers. Except in programming mode this pin is always an output and will be

referred to as “OUT”. In programming mode this pin will be referred to as “IN”.

USER-PROGRAMMABLE REGISTERS

The following registers can be programmed by the user to determine device operating frequency and

mode of operation. Details of how these registers are programmed can be found in a later section; in this

section 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 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 prescaler values and the “DIV” word sets the value of the programmable divider.

MUX WORD Figure 2

(MSB)

(LSB)

0*

0*

0*

1*

1*

M

MSEL

DIV1

0*

*These bits must be set to the indicated values

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-

Table 2

DIV1

BIT

MSEL

BIT

M

BIT

OPERATION

0

0

0

INTERNAL OSCILLATOR DIVIDED BY 4*N

0

0

1

INTERNAL OSCILLATOR DIVIDED BY 2*N

0

1

X

INTERNAL OSCILLATOR DIVIDED BY N