PIC16F72 HS oscillation mode does not vibrate

Thread Starter

sheng Ke

Joined Jun 23, 2019
PIC16F72 in HS mode, with 16M quartz crystal can not start, MCU 5V power supply, the configuration word is: __CONFIG (3FBAh), the same as the 16.000MHz quartz crystal problem does not start, matching capacitor 10p, 12p, 20p, 30p, Crystal two feet and 120K, 300K, 1M resistors have tried, still can not vibration, what is the problem with the master?


Joined Jan 6, 2004
Are you sure that the hex code 3FBA is the actual value?

Personally I've never used the hex values to set anythting in the PICs. I do it as below (not even sure for what micro, taken at random from my files):

Settings PIC.gif
It hardly failed.



Joined Jan 18, 2008
I use MPLAB 8.92 and see there are very limited options for hardware debugging. Moreover, there is not an oscillator ready bit that can be checked.

How are you determining that the oscillator is not running?

When faced with a similar problem, I will set a digital I/O pin to output very early in the program (i.e., before any complicated stuff or loops where it can get stuck, disable interrupts) and put an led on it. Then loop to stop further steps. That serves to indicate the oscillator is running in the absence of an oscillator ready bit I can check


Joined Jan 18, 2008
Register 11 is the Config bits, Xt or Hs
Yes, and I believe it is set according to what the TS said: 0x3FBA = (in part) CP off, PWRTEN disabled, WDT disabled, HS oscillator. If it is not oscillating, the PWRTEN setting (1024 oscillations must occur, no 72 ms timer set), should stop processing.