DSPIC33EP128GS708 datasheet(190/484 Pages) MICROCHIP

190 / 484 page

dsPIC33EPXXXGS70X/80X FAMILY

DS70005258C-page 190

 2016-2018 Microchip Technology Inc.

16.2.1

WRITE-PROTECTED REGISTERS

On dsPIC33EPXXXGS70X/80X family devices, write

protection is implemented for the IOCONx and FCLCONx

registers. The write protection feature prevents any inad-

vertent writes to these registers. This protection feature

can be controlled by the PWMLOCK Configuration bit

(FDEVOPT<0>). The default state of the write protection

feature is enabled (PWMLOCK = 1). The write protection

feature can be disabled by configuring PWMLOCK = 0.

To gain write access to these locked registers, the user

application must write two consecutive values (0xABCD

and 0x4321) to the PWMKEY register to perform the

unlock operation. The write access to the IOCONx or

FCLCONx registers must be the next SFR access

following the unlock process. There can be no other SFR

accesses during the unlock process and subsequent

write access. To write to both the IOCONx and

FCLCONx registers requires two unlock operations.

The correct unlocking sequence is described in

Example 16-1.

EXAMPLE 16-1:

PWM WRITE-PROTECTED REGISTER UNLOCK SEQUENCE

16.3

PWM Resources

Many useful resources are provided on the main prod-

uct page of the Microchip website for the devices listed

in this data sheet. This product page contains the latest

updates and additional information.

16.3.1

KEY RESOURCES

• “High-Speed PWM Module” (DS70000323) in

the “dsPIC33/PIC24 Family Reference Manual”

• Code Samples

• Application Notes

• Software Libraries

• Webinars

• All Related “dsPIC33/PIC24 Family Reference

Manual” Sections

• Development Tools

; Writing to FCLCON1 register requires unlock sequence

mov #0xabcd, w10

; Load first unlock key to w10 register

mov #0x4321, w11

; Load second unlock key to w11 register

mov #0x0000, w0

; Load desired value of FCLCON1 register in w0

mov w10, PWMKEY

; Write first unlock key to PWMKEY register

mov w11, PWMKEY

; Write second unlock key to PWMKEY register

mov w0, FCLCON1

; Write desired value to FCLCON1 register

; Set PWM ownership and polarity using the IOCON1 register

; Writing to IOCON1 register requires unlock sequence

mov #0xabcd, w10

; Load first unlock key to w10 register

mov #0x4321, w11

; Load second unlock key to w11 register

mov #0xF000, w0

; Load desired value of IOCON1 register in w0

mov w10, PWMKEY

; Write first unlock key to PWMKEY register

mov w11, PWMKEY

; Write second unlock key to PWMKEY register

mov w0, IOCON1

; Write desired value to IOCON1 register

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