Preliminary Data Sheet #: TM048

Page 8 of 24

Rev: P00

Date: 05/13/04

Manual Mode

During manual operation, the mode of operation is determined by the user through either the external control pins CNTRL3:1 or

internal configuration bits CF3:1 (see Table 7). The default configuration is to have external control, but this can be changed to

internal control by setting the INT bit the memory-mapped registers via the SPI por t. During manual operation, the user can select

Free Run, Hold Over, or locked operation. Any of the six input references can be selected for the unit to track.

If the module is locked to a reference and that reference becomes disqualified, the module will automatically go into Hold Over.

If the module has been phase-locked to the current reference for at least 50 seconds and is in the final stage of the filter (as

indicated in register 0Eh), the Hold Over value will be derived from the data from the current reference. If the module has been

phase-locked to the current reference for less than 50 seconds, then the last valid Hold Over value will be used. If the control bits/

pins remain in the same selection that caused the unit to go into Hold Over, the unit will remain in Hold Over until the reference is re-

qualified. At that time, after a minimum 10s soak time, the unit will attempt to relock to the same reference.

If the external user control pins select a new reference that the module has not qualified, the module will switch into the last valid

Hold Over value. If the module has not yet established a valid Hold Over, the module will return to the pre-programmed Free Run

value. As soon as the module qualifies the selected reference, it will begin the locking process.

At no time during manual mode will the unit attempt to lock to a reference that is not selected by the external pins/internal bits.

The only mode that the unit will enter automatically is into Hold Over or Free Run, and that is due to a disqualification of the

selected reference.

Fast Acquisition

Lock

Free Run

Hold Over

User selects Hold Over

Use

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Run or resets Hold

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Manual Mode State Diagram

Figure 4