Follow the steps is an example for PIC12F629 OSCCAL value update:
1. Download the Re6.16 OR later version software. 2. Uninstall old version and install the Re6.16 3. Select PIC12F629 chip from software. 4. Click on Erase button in software 6. The erase window will pop up and write down the current OSCCAL value. 7. check the Erase OSCCAL checkbox in the window and click OK to erase the chip. 8. After erase completed, click on CFG button of the software, then the CFG Word Configuration Window pop up. 9. in DDMA area, input 7FF in Address From box and 2 in Length In Byte box. (Here the 7FF is PIC12F629 OSCCAL data byte address. (3FF x 2 + 1= 7FF) From PIC12F629 datasheet, the OSCCAL word address is 3FF. 10. click on Read button. The DDMA should show 3FFF. This is current OSCCAL value. 11. Move the cursor and change the value you wanted. 12. click on Write to write the new OSCCAL data. 13. click on Read to confirm the OSCCAL is updated.