overclocking 28X1
- Thread starter drew45
- Start date
BeanieBots
Moderator
It's really an Either / Or function.
Either, change the resonator to 8Mhz.
Or, remove the resonator and use the internal clock (4Mhz) with setfrequency.
Either, change the resonator to 8Mhz.
Or, remove the resonator and use the internal clock (4Mhz) with setfrequency.
inglewoodpete
Senior Member
From (my) memory, the 28X can't run without an external resonator. The 28X1 can use either the internal or an external resonator.
Edit: ...and then I read the title. It's actually a 28X1, not 28X and mentioned of the detail. ~sigh~
Edit: ...and then I read the title. It's actually a 28X1, not 28X and mentioned of the detail. ~sigh~
westaust55
Moderator
28X1 or 28X
For the 28X1 (but not the 28X) use the command SETFREQ m8 to operate at 8MHz using the internal resonator/clock. No neet to use/change the external resonator as it has an internal resonator. But note that there is provision to use an external resonator if you wish.
The SETFREQ command is not available for the 28X. As IWP says and as per page 145 of the microchip PIC16F873A datasheet, the 28X always requires an external resonator or other suitable external circuit).
That would explain why the AXE022 proto-board comes with a 4MHz resonator as standard. If that is the board you have, then just solder in an 8MHz resonator and move the two jumpers on the proto-board.
Is it a PICAXE 28X1 as per the post title or a 28X as per the words of the post?
For the 28X1 (but not the 28X) use the command SETFREQ m8 to operate at 8MHz using the internal resonator/clock. No neet to use/change the external resonator as it has an internal resonator. But note that there is provision to use an external resonator if you wish.
The SETFREQ command is not available for the 28X. As IWP says and as per page 145 of the microchip PIC16F873A datasheet, the 28X always requires an external resonator or other suitable external circuit).
That would explain why the AXE022 proto-board comes with a 4MHz resonator as standard. If that is the board you have, then just solder in an 8MHz resonator and move the two jumpers on the proto-board.
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westaust55
Moderator
You do not need to change the resonator. There is room on the baord for a second resonator and two jumpers to move to use each as desired.
See the attached diagram
See the attached diagram
Attachments
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hippy
Ex-Staff (retired)
Also, if it is a 28X1 you do not have to change anything to run at 8MHz using the internal oscillator - just use "SETFREQ M8" at the start of your program. It will operate at 8MHz regardless of whether an external resonator is connected or not, regardless of external resonator value.
For the 28X an external 4MHz or 8MHz crystal or resonator must be used.
As westaust55 points out, the AXE022 board allows two resonators to be fitted and jumpers allow either to be selected as desired.
For the 28X an external 4MHz or 8MHz crystal or resonator must be used.
As westaust55 points out, the AXE022 board allows two resonators to be fitted and jumpers allow either to be selected as desired.