SI5338 Datasheet, PDF (20/170 Pages) Silicon Laboratories – I2C-PROGRAMMABLE ANY-FREQUENCY, ANY-OUTPUT QUAD CLOCK GENERATOR

Si5338
3.5.1. Ordering a Custom NVM Configuration
The Si5338 is orderable with a factory-programmed
custom NVM configuration. This is the simplest way of
using the Si5338 since it generates the desired output
frequencies at power-up or after a power-on reset
(POR). This default configuration can be reconfigured in
RAM through the I²C interface after power-up (see
“3.5.2. Creating a New Configuration for RAM”).
The first step in ordering a custom device is generating
an NVM file which defines the input and output clock
frequencies and signal formats. This is easily done
using the ClockBuilder Desktop software (see "3.1.1.
ClockBuilder™ Desktop Software" on page 16). This
GUI based software generates an NVM file, which is
used by the factory to manufacture custom parts. Each
custom part is marked with a unique part number
identifying the specific configuration (e.g., Si5338C-
A00100-GM). Consult your local sales representative
for more details on ordering a custom Si5338.
3.5.2. Creating a New Configuration for RAM
Any Si5338 device can be configured by writing to
registers in RAM through the I²C interface. A non-
factory programmed device must be configured in this
manner.
When writing a configuration to RAM, use the following
procedure:
1. Create a device configuration (register map) using
ClockBuilder Desktop (v2.7 or later; see "3.1.1.
ClockBuilder™ Desktop Software" on page 16) or
manually using the equations in “AN411: Configuring
the Si5338”.
a. Configure the frequency plan.
b. Configure the output driver format and supply
voltage.
c. Configure frequency and/or phase inc/dec (if
desired).
d. Configure spread spectrum (if desired).
e. Configure for zero-delay mode (if desired,
see "3.9.5. Zero-Delay Mode" on page 24).
f. If needed go to the Advanced tab and make
additional configurations.
2. Save the configuration using the Options > Save
Register Map File or Options > Save C code Header
File, or create the register contents by the
conversions listed in AN411.
3.5.3. Writing a Custom Configuration to RAM
Writing a new configuration (register map) to the RAM
consists of pausing the LOL state-machine, writing new
values to the IC accounting for the write-allowed mask
given in "6.1. Register Write-Allowed Mask" on page 28,
validating the input clock or crystal, locking the PLL to
the input with the new configuration, restarting the LOL
state-machine, and calibrating the VCO for robust
operation across temperature. The flow chart in
Figure 9 on page 21 enumerates the details:
Note: The write-allowed mask specifies which bits must be
read and modified before writing the entire register
byte (a.k.a. read-modify-write). “AN428: Jump Start: In-
System, Flash-Based Programming for Silicon Labs’
Timing Products” illustrates the procedure defined in
Section 3.5.2 with ANSI C code.
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