iCE40 Oscillator Usage Guide
Technical Note
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FPGA-TN-02008-1.7
5
1.
Introduction
The iCE40™ family, specifically iCE40 Ultra™, iCE40 UltraLite™ and iCE40 UltraPlus™, features two on-chip oscillators.
An ultra-low power 10 kHz oscillator is provided for Always-On applications and background polling that allow higher
power processors to remain in power-down or sleep mode, conserving overall power consumption. A low power 48
MHz oscillator with output divider is provided for sensor management and pre-processing functions. These oscillators
are intended for general clocking of internal logic and state machines.
This document provides guidance to software engineers on integrating these two oscillator types using iCEcube2™ or
Lattice Radiant™ Software.
1.1.
Key Features
The following oscillators are available to iCEcube2 users:
SB_LFOSC – Low Frequency Oscillator
SB_HFOSC – High Frequency Oscillator with output divider
The following oscillators are available to Lattice Radiant Software users:
LSOSC – Low Frequency Oscillator
HSOSC – High Frequency Oscillator with output divider
2.
On-Chip Oscillator Overview
You can access the two modules: SB_LFOSC and SB_HSOSC with enabled inputs and which you can dynamically control
as shown in
SB_LFOSC runs at 10 kHz and SB_HFOSC runs at maximum 48 MHz with output divider by 1, 2, 4 or 8. SB_LFOSC and
SB_HFOSC provide internal clock sources to user designs. These clocks can directly route to the global clock network or
to local fabric.
SB_HFOSC/HSOSC
CLKHF
CLKHFEN
CLKHFPU
SB_LFOSC/LSOSC
CLKLF
CLKLFEN
CLKLFPU
Figure 2.1. On-Chip Oscillator
