DS1073 Просмотр технического описания (PDF) - Dallas Semiconductor -> Maxim Integrated

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DS1073

3V EconOscillator/Divider

Dallas Semiconductor -> Maxim Integrated 

DS1073

USER-PROGRAMMABLE REGISTERS

The following registers can be programmed by the user to determine 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 non-volatile, 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)

0*

0*

0*

*These bits must be set to 0

(LSB)

EN0

PDN

M

MSEL

DIV1

E/ I

E/ I

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 0 the E/ I bit will be overridden by the logic level on the PDN / SELX pin.

Table 1

PDN

BIT

0

0

1

1

1

( PDN / SELX

E/ I

PIN

OSCILLATOR MODE

X

0

EXTERNAL/CRYSTAL

X

1

INTERNAL

X

0

POWER-DOWN

0

1

INTERNAL

1

1

EXTERNAL/CRYSTAL

DIV1

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

divider is bypassed so the programmed value of N is ignored. The frequency of the output (fOUT) will be

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

the M prescaler may still be used, so in this case fOUT = INTOSC/M (which also equals MCLK and

INTCLK). If DIV1 = 0 the programmable divider functions normally.

MSEL

This bit determines whether or not the M prescaler is bypassed. MSEL = 1 will bypass the prescaler.

MSEL = 0 will switch in the prescaler, 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-

by-2. The setting of this bit is irrelevant if MSEL = 1.

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