NXP Semiconductors S32G2 User manual

S32G2 Vehicle Network Processor - Clock

Configuration Guide

by: NXP Semiconductors

1.Introduction

NXP’s S32G2 is a family of high-performance

vehicle network processors that combines Controller

Area Network (CAN), Local Interconnect Network

(LIN), and FlexRay networking with high-data-rate

Ethernet networking. It also combines a functional

safe-core infrastructure with MPU cores and includes

high-level security features.

S32G2 supports multiple clock sources for clock

generation:

•Fast Internal RC Oscillator (FIRC) (48 MHz)

•Slow Internal RC Oscillator (SIRC) (32 KHz)

•Fast External Crystal Oscillator (FXOSC) (20

–40 MHz)

•Phase-Locked Loops (PLLs)

•Digital Frequency Synthesizer (DFS) modules

This application note is intended to provide the user

values for commonly used PLL/DFS configurations.

This document is accompanied with an attached clock

configurator - S32G2_Clock_Configurator.xlsx. The

calculator simplifies the clock configuration process

by helping user find the recommended and validated

values of PLL parameters (MFI, MFN and DIV), DFS

parameters (MFI and MFN), MC_CGM parameters

NXP Semiconductors

Document Number: AN13354

Application Notes

Rev. 1

11/2021

Contents

1. Introduction....................................................................1

2. PLL................................................................................2

3. DFS................................................................................4

4. Clock calculator design...................................................6

4.1 Options tab........................................................... 6

4.2 Configuration tab.................................................. 7

4.3 Spread spectrum tab.............................................. 8

4.4 Clock calculator key considerations....................... 9

5. Spread Spectrum........................................................... 10

5.1 Frequency modulation programming................... 10

5.2 Spread Spectrum Considerations......................... 11

5.3 Example code..................................................... 12

6Clock Configuration using S32DS Clocks Tool.............. 13

7References.................................................................... 15

PLL

S32G2 Vehicle Network Processor - Clock Configuration Guide, Rev. 1, 11/2021

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(SELCTL and DIV) to achieve the target clock frequency along with the calculation of STEPNO and

STEPSIZE for programming modulation depth and modulation frequency.

This document complements the S32G2 Reference Manual1and S32G2 Data Sheet2. Readers are

advised to read through “Clocking” chapter from S32G2 Reference Manual1before further diving into

this document.

The following table shows the abbreviations used throughout the document.

Table1. Acronyms and abbreviations

Abbreviation

Explanation

DFS

Digital Frequency Synthesizer

EMI

Electromagnetic Interference

FIRC

Fast Internal RC Oscillator

fMOD

Modulation Frequency

fPLL_VCO

PLL VCO frequency with SSCG enabled

fREF

PLL Reference Clock

FXOSC

Fast External Crystal Oscillator

LDF

Loop Division Factor

Modulation Depth

PLL

Phase Locked Loop

SSCG

Spread Spectrum Clock Generation

2.PLL

The document provides the coherent values for the following PLLs:

1. CORE_PLL

2. PERIPH_PLL

3. ACCEL_PLL

4. DDR_PLL

PLL

S32G2 Vehicle Network Processor - Clock Configuration Guide, Rev. 1, 11/2021

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Figure 1. PLL block diagram

The user need to configure the value for below parameters to achieve the target frequencies for

PLL_VCO and PLL_PHIn.

1. Reference clock : Clock sources for the PLLs can either be the 20 –40 MHz FXOSC or 48 MHz

FIRC. During boot, FIRC_CLK is used as the default PLL reference clock. After boot, the PLL

reference must be changed to FXOSC_CLK. Ensure that PLLCLKMUX[REFCLKSEL] is

selected accordingly.

RDIV : PLL input reference clock frequency after pre-divider should be between 20 –40 MHz,

therefore the valid values for RDIV are shown in the following table.

Table2. RDIV values

Frequency

RDIV

FXOSC –20 MHz

FXOSC –24 MHz

FXOSC –40 MHz

1 or 2

FIRC –48 MHz

DFS

S32G2 Vehicle Network Processor - Clock Configuration Guide, Rev. 1, 11/2021

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NOTE

For a crystal of 40 MHz, NXP recommends using RDIV = 1 for better

jitter performance.

2. MFI : Integer part of LDF

3. MFN : Numerator of fractional LDF

4. DIV : Division value

5. STEPSIZE : Step size for modulation depth and frequency in frequency modulation mode

6. STEPNO : Number of steps to achieve modulation depth in frequency modulation mode.

3.DFS

The document provides the coherent values for following DFS:

1. CORE_DFS

2. PERIPH_DFS

DFS

S32G2 Vehicle Network Processor - Clock Configuration Guide, Rev. 1, 11/2021

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Figure 2. DFS block diagram

The user needs to configure the value for the below parameters to achieve the target frequencies for

CORE_DFSn and PERIPH_DFSn.

1. PLL_VCO : Respective PLL_VCO frequency serves an input clock source to the DFS block.

2. MFI : Integer part of LDF.

3. MFN : Numerator of fractional LDF

Clock calculator design

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4.Clock calculator design

The S32G2 clock configurator is in the form of an interactive Microsoft Excel spreadsheet organized in

multiple tabs as explained in below sub-sections.

4.1 Options tab

The options tab provides an interface to select the following:

1. FXOSC frequency

Figure 3. Selecting FXOSC frequency

2. RDIV –RDIV is selected individually for each PLL : CORE_PLL, PERIPH_PLL,

ACCEL_PLL, DDR_PLL.

Figure 4. Selecting RDIV value

RDIV must be selected to ensure that the input frequency of each PLL is between 20 –40 MHz.

3. Option to enable/disable SSCG for CORE_PLL, ACCEL_PLL and DDR_PLL.

Figure 5. Enabling/Disabling SSCG

4. Clock Source –Select the clock source.

Figure 6. Selecting the clock source

Clock calculator design

S32G2 Vehicle Network Processor - Clock Configuration Guide, Rev. 1, 11/2021

NXP Semiconductors 7

5. Target Frequency –Select the target frequency.

Figure 7. Selecting the clock frequency

In case of CORE_PLL, DDR_PLL, ACCEL_PLL, the sheet lists a set of frequencies to support

the SSCG disabled case and the corresponding set of frequencies with 1.5% modulation depth

for SSCG enabled case.

As an example for A53_CORE_CLK : In case SSCG is disabled, the calculator provides 500

MHz, 800 MHz and 1000 MHz frequency options.

Figure 8. FA53_CORE_CLK with SSCG disabled

And when SSCG modulation is enabled, the calculator provides frequency options with 1.5%

modulation depth - 496.3 MHz, 794 MHz, 992.5 MHz.

Figure 9. FA53_CORE_CLK with SSCG enabled

4.2 Configuration tab

After selecting the parameters in the options tab, the calculator provides the value for PLL parameters

(MFI, MFN, DIV), DFS parameters (MFI, MFN) and MC_CGM parameters (SELCTL, DIV) in the

configurations tab on the basis of the selection in the options tab.

Clock calculator design

S32G2 Vehicle Network Processor - Clock Configuration Guide, Rev. 1, 11/2021

8 NXP Semiconductors

As an example if the user selects the clock source for CAN_PE_CLK as PLL and 40 MHz as the target

frequency with RDIV and FXOSC value as 1 and 40 MHz respectively, the configuration tab provides

the values for clocking parameters as shown in the following image.

Figure 10. Configurations as per the selected parameters

4.3 Spread spectrum tab

With the help of this tab user can calculate values for STEPNO and STEPSIZE to program the

modulation depth and the modulation frequency.

The calculator takes the below input parameters:

1. VCO frequency with SSCG disabled

2. Reference frequency

3. RDIV

4. Modulation frequency

5. Modulation depth

User needs to enter the value for VCO frequency with SSCG disabled, modulation frequency and

modulation depth and select reference frequency and RDIV from the drop down list.

An example to calculate STEPNO and STEPSIZE for the CORE_PLL is shown below.

Figure 11. Spread spectrum tab

Clock calculator design

S32G2 Vehicle Network Processor - Clock Configuration Guide, Rev. 1, 11/2021

NXP Semiconductors 9

4.4 Clock calculator key considerations

1. RDIV –User must ensure that RDIV value remains in range when selecting or changing a

FXOSC frequency and manually update the RDIV value such that an invalid option is not

selected for the FXOSC frequency.

As an example, if the initial values for FXOSC and RDIV are selected as 40 MHz and 2

respectively and the user update the FXOSC frequency to 20 MHz, the RDIV block turns pink to

indicate the RDIV holds an invalid option for the selected FXOSC frequency. Therefore, the user

must correct the RDIV value in case the FXOSC frequency is updated.

Figure 12. Invalid RDIV error

Same precaution needs to be taken care while updating the FXOSC frequency in Spread

Spectrum tab.

2. Target frequency –As explained above, caution needs to be exercised while enabling or

disabling the SSCG mode. User should manually update the frequency when SSCG mode is

updated.

As an example, if Spread Spectrum is enabled for DDR_PLL and DDR_CLK is selected as 794

MHz and the user disables the spread spectrum, the FDDR_CLK block turns pink to indicate user to

update the FDDR_CLK from the list of frequencies in SSCG disabled mode.

Figure 13. Frequency update error

3. In the Spread Spectrum tab, user must ensure that the specified value for VCO frequency with

SSCG disabled, Modulation frequency and Modulation depth are within range as specified in

section Spread Spectrum Considerations.

Any invalid value selection leads to the specified parameter block turning pink. User must adjust

the value of specified parameter to be within range.

Spread spectrum

S32G2 Vehicle Network Processor - Clock Configuration Guide, Rev. 1, 11/2021

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Figure 14. VCO frequency out of specified range

5. Spread spectrum

Spread Spectrum clocking is a technique used in electronic design to intentionally modulate the ideal

position of the clock edge such that the resulting signal’s spectrum is “spread” around the ideal

frequency of the clock. Spread Spectrum clocking is often used to help meet the regulated EMI

requirements.

This section provides the user instructions on how to enable Spread Spectrum functionality.

For S32G2, Spread Spectrum clock modulation is only available for the Core, Accelerator and DDR

PLLs.

PLL operates in frequency modulation mode when the user sets the following bits as shown in the table

below –

Table 3. Mode to enable spread spectrum

PLLCR[PLLPD]

PLLFD[SDMEN]

PLLFM[SSCGBYP]

PLLFM[SPREADCTL]

5.1 Frequency modulation programming

Modulation depth and modulation frequency programming uses step number (PLLFM[STEPNO]) and

step size (PLLFM[STEPSIZE]) which can be calculated by using the below equations:

󰇟󰇠  

    󰇟󰇠

Equation 1

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