Si5345-44-42-D-RM
14
Rev. 1.0
4. Modes of Operation
After initialization the DSPLL will operate in one of the following modes: Free-run, lock-acquisition, locked, or
holdover. See Figure 3 below for the state diagram showing the modes of operation. The following sections
describe each of these modes in greater detail.
Figure 3. Modes of Operation
4.1. Reset and Initialization
Once power is applied, the device begins an initialization period where it downloads default register values and
configuration data from NVM and performs other initialization tasks. Communicating with the device through the
serial interface is possible once this initialization period is complete. No clocks will be generated until initialization is
complete.
There are two types of resets available. A hard reset is functionally similar to a device power-up. All registers are
restored to the values stored in NVM, and all circuits, including the serial interface, are restored to their initial state.
A hard reset is initiated using the RST pin or by asserting the hard reset bit. A soft reset bypasses the NVM
download. It is simply used to initiate register configuration changes. Table 5 lists the reset and control registers.
No valid
input clocks
selected
Lock Acquisition
(Fast Lock)
Locked
Mode
Holdover
Mode
Phase lock on
selected input
clock is achieved
Selected input
clock fails
An input is qualified
and available for
selection
Ye
s
Free-run
Valid input clock
selected
Reset and
Initialization
Power-Up
Is holdover
history valid?
No