pic24_clockfreq.h File Reference

Configures the system clock. More...

#include <stdint.h>
#include "pic24_chip.h"
#include "pic24_libconfig.h"

Go to the source code of this file.

Macros
#define	CYCLES_PER_MS   ((uint32_t)(FCY * 0.001))
#define	CYCLES_PER_US   ((uint32_t)(FCY * 0.000001))
#defines for CLOCK_CONFIG
#define	SIM_CLOCK   0, -1, 1000000L, POSCMD_NONE, -1, configClockSim, 1, 498
#define	FRCPLL_FCY16MHz   1, FNOSC_FRCPLL, 16000000L, POSCMD_NONE, -1, configClockFRCPLL_FCY16MHz, (PIC24F_DEFINED || PIC24FK_DEFINED), 498
#define	FRC_FCY4MHz   2, FNOSC_FRC, 4000000L, POSCMD_NONE, -1, configClockFRC_FCY4MHz, (PIC24F_DEFINED || PIC24FK_DEFINED), 498
#define	PRI_NO_PLL_7372KHzCrystal   3, FNOSC_PRI, 3686400L, POSCMD_XT, 7372800L, configClockPRI_NO_PLL_7372KHzCrystal, (PIC24F_DEFINED || PIC24FK_DEFINED || PIC24H_DEFINED || dsPIC33F_DEFINED), 498
#define	FRC_FCY3685KHz   4, FNOSC_FRC, 3685000L, POSCMD_NONE, -1, configClockFRC_FCY3685KHz, (PIC24E_DEFINED || dsPIC33E_DEFINED || PIC24H_DEFINED || dsPIC33F_DEFINED), 498
#define	FRCPLL_FCY40MHz   5, FNOSC_FRCPLL, 40000000L, POSCMD_NONE, -1, configClockFRCPLL_FCY40MHz, (PIC24E_DEFINED || dsPIC33E_DEFINED || PIC24H_DEFINED || dsPIC33F_DEFINED), 498
#define	PRIPLL_7372KHzCrystal_40MHzFCY   6, FNOSC_PRIPLL, 39920833L, POSCMD_XT, 7372800L, configClockPRIPLL_7372KHzCrystal_40MHzFCY, (PIC24H_DEFINED || dsPIC33F_DEFINED), 498
#define	PRIPLL_8MHzCrystal_40MHzFCY   7, FNOSC_PRIPLL, 40000000L, POSCMD_XT, 8000000L, configClockPRIPLL_8MHzCrystal_40MHzFCY, (PIC24H_DEFINED || dsPIC33F_DEFINED || PIC24E_DEFINED || dsPIC33E_DEFINED), 498
#define	PRIPLL_8MHzCrystal_16MHzFCY   8, FNOSC_PRIPLL, 16000000L, POSCMD_XT, 8000000L, configClockPRIPLL_8MHzCrystal_16MHzFCY, (PIC24F_DEFINED || PIC24FK_DEFINED), 498
#define	PRI_8MHzCrystal_4MHzFCY   9, FNOSC_PRI, 4000000L, POSCMD_XT, 8000000L, configClockPRI_8MHzCrystal_4MHzFCY, (PIC24F_DEFINED || PIC24FK_DEFINED || PIC24H_DEFINED || dsPIC33F_DEFINED || PIC24E_DEFINED || dsPIC33E_DEFINED), 498
#define	FRCPLL_FCY60MHz   10, FNOSC_FRCPLL, 59881250L, POSCMD_NONE, -1, configClockFRCPLL_FCY60MHz, (PIC24E_DEFINED || dsPIC33E_DEFINED), 498
#define	FRCPLL_FCY70MHz   11, FNOSC_FRCPLL, 70015000L, POSCMD_NONE, -1, configClockFRCPLL_FCY70MHz, (PIC24E_DEFINED || dsPIC33E_DEFINED), 498
Some of the #defines produced by CLOCK_CONFIG choice
#define	CLOCK_CONFIG_INDEX   (GET_CLOCK_CONFIG_INDEX(CLOCK_CONFIG))
#define	FNOSC_SEL   (GET_FNOSC_SEL(CLOCK_CONFIG))
#define	FCY   (GET_FCY(CLOCK_CONFIG))
#define	POSCMD_SEL   (GET_POSCMD_SEL(CLOCK_CONFIG))
#define	POSC_FREQ   (GET_POSC_FREQ(CLOCK_CONFIG))
#define	CONFIG_DEFAULT_CLOCK()   (GET_CONFIG_DEFAULT_CLOCK(CLOCK_CONFIG)())
Helper macros for clock configuration
#define	IS_CLOCK_CONFIG(clockConfig)   (_GET_CLOCK_CONFIG_INDEX(clockConfig) == CLOCK_CONFIG_INDEX)
#define	GET_OSC_SEL_BITS(bits)   _GET_OSC_SEL_BITS(bits)
#define	OSC_SEL_BITS   GET_OSC_SEL_BITS(FNOSC_SEL)

Functions
static void	configClock ()
void	switchClock (uint8_t u8_source)

Detailed Description

Configures the system clock.

The clocking options for the PIC24 are chosen in this file. The resulting settings are used in pic24_clockfreq.c to configure and switch the oscillator as necessary after the chip is running.

To choose a clock configuration, simply select a value for CLOCK_CONFIG from the table there. The default selection used by most of the PIC24H examples is FRCPLL_FCY40MHz (the internal FRC+PLL configured for FCY = 40 MHz). Some of the examples in Chapter 12 expect an external 8 MHz crystal, and use the PRIPLL_8MHzCrystal_40MHzFCY option (external 8 MHz crystal + PLL confgured for FCY = 40 MHz).

This file provides several useful defines as a result of the clock selection above:

• CLOCK_CONFIG itself, although this is not typically directly useful. To determine which clock configuration was chosen, use the CLOCK_CONFIG_INDEX for comparsion by applying the IS_CLOCK_CONFIG macro.
• The oscillator source as a configuration word (FNOSC_SEL) and as a COSC/NOSC bitfield in the OSCCON register (OSC_SEL_BITS).
• The processor clock frequency FCY.
• The primary oscillator type POSCMD_SEL.
• The primary oscillator freqency POSC_FREQ.

To define a new clock configuation:

• Add a #define to the table (see the section "#defines for CLOCK_CONFIG").
• Add a configClockXxx() function which sets up and typically switches to that clock in pic24_clockfreq.c and a prototype for that function in this file.

Definition in file pic24_clockfreq.h.

Macro Definition Documentation

CLOCK_CONFIG_INDEX

#define CLOCK_CONFIG_INDEX   (GET_CLOCK_CONFIG_INDEX(CLOCK_CONFIG))

A unique number is assigned to each clock configuration, in order to allow comparsions between configurations. CLOCK_CONFIG_INDEX gives the number assigned to the selected clock configuration. The macro IS_CLOCK_CONFIG uses this number for its comparsisons.

See also

SIM_CLOCK

CONFIG_DEFAULT_CLOCK

#define CONFIG_DEFAULT_CLOCK

(

)

(GET_CONFIG_DEFAULT_CLOCK(CLOCK_CONFIG)())

Calls one of the configClock() functions defined in pic24_clockfreq.c based on the CLOCK_CONFIG chosen.

Referenced by configClock().

CYCLES_PER_MS

#define CYCLES_PER_MS   ((uint32_t)(FCY * 0.001))

A constant which gives the number of processor clock cycles in 1 millisecond. This value is cast to a uint32_t.

Definition at line 332 of file pic24_clockfreq.h.

CYCLES_PER_US

#define CYCLES_PER_US   ((uint32_t)(FCY * 0.000001))

A constant which gives the number of processor clock cycles in 1 microsecond. This value is cast to a uint32_t.

Definition at line 338 of file pic24_clockfreq.h.

FCY

#define FCY   (GET_FCY(CLOCK_CONFIG))

FCY specifies the resulting processor clock frequency after all PLL/divide operations take the inital clock and produce a processor clock. The units of this value are Hz, so the value 40000000L is 40 MHz.

NOTE: This should be defined as a long (with a trailing L after the number) to allocate enough space to correctly store the processor clock frequency.

Referenced by CONFIG_BAUDRATE_UART1(), configI2C1(), configUART1(), esos_pic24_configI2C1(), msToU16Ticks(), ticksToMs(), ticksToNs(), ticksToUs(), usToU16Ticks(), and usToU32Ticks().

FNOSC_SEL

#define FNOSC_SEL   (GET_FNOSC_SEL(CLOCK_CONFIG))

Oscillator source selection for the PIC24. FNOSC_SEL is set to one of the following based on CLOCK_CONFIG :

Name                 Description                                   PIC24F  PIC24FK  PIC24H/dsPIC33F  PIC24E/dsPIC33E
-------------        --------------------------------------------  ------  -------  ---------------  ---------------
FNOSC_FRC            Fast RC oscillator                               X        X           X               X
FNOSC_FRCPLL         Fast RC oscillator w/ divide and PLL             X        X           X               X
FNOSC_PRI            Primary oscillator (XT, HS, EC)                  X        X           X               X
FNOSC_PRIPLL         Primary oscillator (XT, HS, EC) w/ PLL           X        X           X               X
FNOSC_SOSC           Secondary oscillator                             X        X           X               X
FNOSC_LPRC           Low power RC oscillator                          X        X           X               X
FNOSC_FRCDIV16       Fast RC oscillator w/ divide by 16                                    X               X
FNOSC_LPRCDIVN       Low power RC oscillator w/divide by N                                 X               X
FNOSC_LPFRCDIV       500 kHz FRC Oscillator with Postscaler                    X
FNOSC_FRCDIV         Fast RC oscillator with divide                   X        X

GET_OSC_SEL_BITS

#define GET_OSC_SEL_BITS

(

bits

)

_GET_OSC_SEL_BITS(bits)

A macro to determine the NOSC/COSC bits for the OSCCON register given bits taken from the PIC24's configuration FNOSC word.

Definition at line 359 of file pic24_clockfreq.h.

IS_CLOCK_CONFIG

#define IS_CLOCK_CONFIG

(

clockConfig

)

(_GET_CLOCK_CONFIG_INDEX(clockConfig) == CLOCK_CONFIG_INDEX)

A helper macro to check if the given clock configuration was selected. Example usage is given in pic24_clockfreq.c. A shorter example:

#if IS_CLOCK_CONFIG(FRCPLL_FCY40MHz)
... code only included if CLOCK_CONFIG is FRCPLL_FCY40MHz ...
#endif

Parameters

clockConfig

Clock configuration to compare the current clock configuation against.

Definition at line 353 of file pic24_clockfreq.h.

OSC_SEL_BITS

#define OSC_SEL_BITS   GET_OSC_SEL_BITS(FNOSC_SEL)

A macro giving the NOSC/COSC bits for the OSCCON register which correspond to FNOSC_SEL, the configuration word which contains the FNOSC bits.

Definition at line 372 of file pic24_clockfreq.h.

POSC_FREQ

#define POSC_FREQ   (GET_POSC_FREQ(CLOCK_CONFIG))

This values gives the primary osciallator frequency (if used). The units of this value are Hz, so the value 40000000L is 40 MHz.

NOTE: This should be defined as a long (with a trailing L after the number) to allocate enough space to correctly store the processor clock frequency.

POSCMD_SEL

#define POSCMD_SEL   (GET_POSCMD_SEL(CLOCK_CONFIG))

Specifies the primary oscillator type. Valid values:

POSCMD_EC            External clock
POSCMD_XT            XT oscillator (for crystals from 3.5 MHz to 10 MHz)
POSCMD_HS            HS oscillator (for crystals from 10 MHz to 32 MHz)
POSCMD_NONE          Primary oscillator disabled

SIM_CLOCK

#define SIM_CLOCK   0, -1, 1000000L, POSCMD_NONE, -1, configClockSim, 1, 498

Create a table of vales for CLOCK_CONFIG. When adding a new entry, you must also write C code to configure the clock in pic24_clockfreq.c. See that file for examples and the detailed description section at the top of this page for more information. Note that FCY and POSC_FREQ should be defined as a long (with a trailing L) to retain enough accuracy to store these values.

Table entry notes: (see actual code, not the documentation, for the table)

• Use -1 for don't-care values
• The "unique index" just means each clock configuration should be assigned a different number. Giving two configurations the same index will cause problems!

  See also

  CLOCK_CONFIG_INDEX.

• The processor field should evaluate to a Boolean value which is true if the processor under which this file is compiled is supported. Later in this file, the values PIC24F_DEFINED and PIC24H_DEFINED are set to true (1) or false (0) based on which processor this file is compiled with. Use these values in the Boolean expression. For example:
  • 1 (works on any processor)
  • PIC24H_DEFINED (works only on the PIC24H)
  • PIC24F_DEFINED || PIC24H_DEFINED (works on PIC24F and PIC24H).
• Valid entries for FNOSC_SEL are defined documentation for that variable.

Definition at line 155 of file pic24_clockfreq.h.

Function Documentation

configClock()

static void configClock ( )

inlinestatic

Configure the default clock by calling the CONFIG_DEFAULT_CLOCK() macro.

Definition at line 446 of file pic24_clockfreq.h.

Referenced by configBasic().

switchClock()

void switchClock

(

uint8_t

u8_source

)

Switch the clock to the source specified. The source given will be assigned to NOSC in the OSCCON register, the a switch clock performed.

Note: DO NOT use FNOSC_SEL as the source; instead, use OSC_SEL_BITS. FNOSC_SEL is for configuration bits while switchClock expects a NOSC value to write to the OSCCON register.

Parameters

u8_source

The clock source to switch to.

Definition at line 212 of file pic24_clockfreq.c.

Referenced by configClock().