30 min

Generate high-frequency clock output with ICS501 and PIC18F4680

Phase-Locked Loop (PLL) mechanism

PLL Click with Curiosity HPC

Published Nov 01, 2023

Click board™

PLL Click

Development board

Curiosity HPC


NECTO Studio



Generate highly stable and coherent high-frequency signals for applications requiring tight synchronization and minimal phase noise



Hardware Overview

How does it work?

PLL Click is based on the ICS501, a LOCO™ PLL clock multiplier, from Integrated Device Technology. This IC uses the Phase-Locked Loop to provide a high-frequency clock output, deriving input from a much cheaper, standard fundamental frequency crystal oscillator. Besides the onboard crystal oscillator fixed at 12MHz, it is possible to select the signal from the mikroBUS™ PWM pin as the clock input source. To select the desired multiplication factor, the states of the two input pins, S0 and S1, are routed to the mikroBUS™ pins RST and AN, respectively. These pins can be set to a HIGH or LOW logic state or disconnected (by tri-stating the MCU pins). The combination of these pins states will set the PLL

Click to a specific multiplier. The Output Enable (OE) pin of the ICS501 is used to turn off the output clock by setting it to a LOW logic level. It will additionally set the clock output pin in high impedance (Hi-Z) mode, allowing complete disconnection and no influence on the rest of the circuit, which is useful for experimenting and prototyping purposes. This pin is internally pulled to a HIGH logic level. The OE pin is routed to the CS pin of the mikroBUS™. PLL Click is equipped with two onboard SMD jumpers. The SMD jumper labeled as the VCC SEL is used to select the operating voltage level, consequently limiting the amplitude of the clock output signal with respect to the selected voltage. The other SMD jumper

labeled as the OSC SEL chooses the clock input source between the onboard 12MHz crystal oscillator or the external clock signal. The output signal is routed through the onboard SMA connector, which provides a secure connection and good signal shielding. PLL Click has a library containing functions for all the MIKROE compilers (mikroBASIC, mikroPASCAL, and mikroC). Although relatively easy to control, the library offers comprehensive functions that make the code readable and easy to use. The included example application demonstrates the use of these functions, and it can be used as a reference for custom projects.

PLL click hardware overview image

Features overview

Development board

Curiosity HPC, standing for Curiosity High Pin Count (HPC) development board, supports 28- and 40-pin 8-bit PIC MCUs specially designed by Microchip for the needs of rapid development of embedded applications. This board has two unique PDIP sockets, surrounded by dual-row expansion headers, allowing connectivity to all pins on the populated PIC MCUs. It also contains a powerful onboard PICkit™ (PKOB), eliminating the need for an external programming/debugging tool, two mikroBUS™ sockets for Click board™ connectivity, a USB connector, a set of indicator LEDs, push button switches and a variable potentiometer. All

these features allow you to combine the strength of Microchip and Mikroe and create custom electronic solutions more efficiently than ever. Each part of the Curiosity HPC development board contains the components necessary for the most efficient operation of the same board. An integrated onboard PICkit™ (PKOB) allows low-voltage programming and in-circuit debugging for all supported devices. When used with the MPLAB® X Integrated Development Environment (IDE, version 3.0 or higher) or MPLAB® Xpress IDE, in-circuit debugging allows users to run, modify, and troubleshoot their custom software and hardware

quickly without the need for additional debugging tools. Besides, it includes a clean and regulated power supply block for the development board via the USB Micro-B connector, alongside all communication methods that mikroBUS™ itself supports. Curiosity HPC development board allows you to create a new application in just a few steps. Natively supported by Microchip software tools, it covers many aspects of prototyping thanks to many number of different Click boards™ (over a thousand boards), the number of which is growing daily.

Curiosity HPC double image

Microcontroller Overview

MCU Card / MCU




MCU Memory (KB)


Silicon Vendor


Pin count


RAM (Bytes)


Used MCU Pins

mikroBUS™ mapper

Multiplier Adjustment
Multiplier Adjustment
Output Enable
Power Supply
External Clock Source
Power Supply

Take a closer look


PLL click Schematic schematic

Step by step

Project assembly

Curiosity HPC front no-mcu image hardware assembly

Start by selecting your development board and Click board™. Begin with the Curiosity HPC as your development board.

Curiosity HPC front no-mcu image hardware assembly
GNSS2 Click front image hardware assembly
MCU DIP 40 hardware assembly
Prog-cut hardware assembly
GNSS2 Click complete accessories setup image hardware assembly
Curiosity HPC Access MB 1 - upright/background hardware assembly
Necto image step 2 hardware assembly
Necto image step 3 hardware assembly
Necto image step 4 hardware assembly
Necto image step 5 hardware assembly
Necto image step 6 hardware assembly
Necto DIP image step 7 hardware assembly
Necto No Display image step 8 hardware assembly
Necto image step 9 hardware assembly
Necto image step 10 hardware assembly
Debug Image Necto Step hardware assembly

Track your results in real time

Application Output

After loading the code example, pressing the "DEBUG" button builds and programs it on the selected setup.

Application Output Step 1

After programming is completed, a header with buttons for various actions available in the IDE appears. By clicking the green "PLAY "button, we start reading the results achieved with Click board™.

Application Output Step 3

Upon completion of programming, the Application Output tab is automatically opened, where the achieved result can be read. In case of an inability to perform the Debug function, check if a proper connection between the MCU used by the setup and the CODEGRIP programmer has been established. A detailed explanation of the CODEGRIP-board connection can be found in the CODEGRIP User Manual. Please find it in the RESOURCES section.

Application Output Step 4

Software Support

Library Description

This library contains API for PLL Click driver.

Key functions:

  • pll_set_clock_output - This function settings clock output

  • pll_set_pll_4x - This function settings PLL x4

  • pll_set_pll_6x - This function settings PLL x6

Open Source

Code example

This example can be found in NECTO Studio. Feel free to download the code, or you can copy the code below.

 * \file 
 * \brief PLL Click example
 * # Description
 * This app sets PLL signals.
 * The demo application is composed of two sections :
 * ## Application Init 
 * Initializes device.
 * ## Application Task  
 * Every 2 seconds, the PLL increases the input clock in the order of x4, x5, x6 and x8.
 * *note:*
 * If you use PLL x4, x5, x6 or x8, set S0 (RST pin) and S1 (AN pin) as OUTPUT.
 * If you use PLL x3.125 or x6.25, set S1 ( AN pin ) as INPUT and S0( RST pin ) as OUTPUT.
 * If you use PLL x3 or x5.3125, set S0 ( RST pin ) as INPUT and S1 ( AN pin ) as OUTPUT.
 * \author MikroE Team
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "pll.h"

// ------------------------------------------------------------------ VARIABLES

static pll_t pll;
static log_t logger;

// ------------------------------------------------------ APPLICATION FUNCTIONS

void application_init ( void )
    log_cfg_t log_cfg;
    pll_cfg_t cfg;

     * Logger initialization.
     * Default baud rate: 115200
     * Default log level: LOG_LEVEL_DEBUG
     * @note If USB_UART_RX and USB_UART_TX 
     * are defined as HAL_PIN_NC, you will 
     * need to define them manually for log to work. 
     * See @b LOG_MAP_USB_UART macro definition for detailed explanation.
    LOG_MAP_USB_UART( log_cfg );
    log_init( &logger, &log_cfg );
    log_info(&logger, "---- Application Init ----");

    //  Click initialization.

    pll_cfg_setup( &cfg );
    pll_init( &pll, &cfg );
    pll_set_clock_output( &pll, PLL_CLOCK_ENABLE );

void application_task ( void )
    pll_set_pll_4x( &pll );
    Delay_ms( 2000 );
    pll_set_pll_5x( &pll );
    Delay_ms( 2000 );
    pll_set_pll_6x( &pll );
    Delay_ms( 2000 );
    pll_set_pll_8x( &pll );
    Delay_ms( 2000 );

void main ( void )
    application_init( );

    for ( ; ; )
        application_task( );

// ------------------------------------------------------------------------ END

Additional Support