AN1360 - Serial Communications and API Programming Guide for Skyworks API-Enabled Timing Devices - Application Note

Nov 2, 2026

Application Note AN1360 explains serial communications and how to use the Device API to load user configuration and firmware onto Skyworks clock and timing products. It provides step-by-step procedures for SPI (3/4-wire) and I2C access, volatile frequency plan loading, and multi-time-programmable NVM bank burn operations, including NVM patch burn steps. Coverage also includes flash write guidance where supported, sample interaction code, an overview of libskytiming, and troubleshooting considerations.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages78

Reading Time3 h 17 min

AccessFree to download

1. The Basics

1.1. Applicable Devices

1.2. Device API and libSkyTiming Introduction

1.3. libSkyTiming C Library

APPLICATION NOTE AN1360: Serial Communications and API Programming Guide for Skyworks API-Enabled Timing Devices Key Points • Accessing the Device Application Programming Interface (Device API) through 3/4-wire SPI and I2C • Step-by-step instructions for loading a volatile frequency plan onto a clock device • Steps for performing a non-volatile memory (NVM) burn over the serial interface • Steps for performing a NVM patch burn over the serial interface • Steps for writing to flash, where supported • Sample code to interact with the clock devices • An overview of libskytiming • Troubleshooting tips Description This application note contains descriptions of serial communications interfaces and the steps for loading a user configuration and firmware onto Skyworks clock and timing products using the Device API. Steps for burning the multi-time-programmable NVM bank and are also included. Skyworks Solutions, Inc. • Phone [949] 231-3000 • [sales@skyworksinc.com](sales@skyworksinc.com) • [www.skyworksinc.com](www.skyworksinc.com)[ ](www.skyworksinc.com)206535E • Skyworks Proprietary Information • Products and Product Information are Subject to Change without Notice 1 June 18, 2025 APPLICATION NOTE AN1360: Serial Communications and API Programming Guide 1. The Basics 1.1. Applicable Devices All devices in the table below share a common Device API implementation and are software-compatible with each other. Table 1. Applicable Devices and Supported Memory Options | Skyworks Timing Devices | Serial Protocols | Volatile Write (RAM), Resets on Power Cycle | Multiple-Time-Programmable (MTP) NVM1 | Flash Supported | | --- | --- | --- | --- | --- | | Si5508/10/12/18 | SPI (4-wire/3-wire), I2C, secondary SPI (3-wire) | Supported | FW v1 .3: one baseline and nine patches
FW v1 .4 and later: one baseline and eight patches | No | | Si5401/2/3 | SPI (4-wire/3-wire), I2C, secondary SPI (3-wire) | Supported | FW v1 .3: one baseline and nine patches
FW v1 .4 and later: one baseline and eight patches | No | | Si5360/1/2/3 | SPI (4-wire/3-wire), I2C | Supported | FW v1 .3: one baseline and nine patches
FW v1 .4 and later: one baseline and eight patches | No | | SKY69001/02 | SPI (4-wire/3-wire), I2C, secondary SPI (3-wire) | Supported | One baseline and seven patches | Yes, internal2 | | SKY69003 | SPI (4-wire/3-wire), I2C | Supported | One baseline and eight patches | Yes, external2 | | SKY69101 | SPI (4-wire/3-wire), I2C, secondary SPI (3-wire) | Supported | One baseline and seven patches | Yes, internal2 | | SKY69102 | SPI (4-wire/3-wire), I2C | Supported | One baseline and eight patches | Yes, external2 | | SKY63001 | SPI (4-wire/3-wire), I2C | Supported | One baseline and eight patches | Yes, external2 | | SKY63101/02/03 | SPI (4-wire/3-wire), I2C | Supported | One baseline and seven patches | Yes, internal2 | | SKY63104/05/06 | SPI (4-wire/3-wire), I2C | Supported | One baseline and eight patches | Yes, external2 | | SKY62101 | SPI (4-wire/3-wire), I2C | Supported | One baseline and eight patches | Yes, external2 | 1. Multiple time programming for baseline burn using FW v1 .3 and later only. Older firmware supports only a single burn, either by the factory or by the user. Actual number of burns depends on remaining memory and may change based on firmware version. 2. Non-Volatile NVM (MTP) and flash are mutually exclusive and cannot be supported simultaneously on the same device. Memory type is set by the part ordering number. Please consult the ordering options section of the device data sheet to ensure a device has the expected memory option 1.2. Device API and libSkyTiming Introduction The clock device supports SPI or I2C for command and control. An on-chip MCU runs the firmware that manages the device. This firmware also provides the “Device API,” which accepts commands and sends replies over the serial interface. The Device API documentation defines the command and reply byte structur

FAQs

What is the Device API used for in these Skyworks timing devices?

The Device API provides a defined command and reply byte structure that an on-chip MCU executes over the serial interface. It enables device functionality without direct register access.

Which serial protocols are supported for accessing the Device API?

The document states support for SPI (4-wire/3-wire, including secondary SPI 3-wire) and I2C, with protocol support varying by device family.

How are volatile plans and non-volatile memory updates performed?

It describes loading a volatile frequency plan via the serial interface and performing NVM burn and NVM patch burn operations over the serial interface. It also notes that non-volatile MTP and flash are mutually exclusive on the same device.

Nov 2, 2026

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