Name:
setfreq
Syntax:

SETFREQ freq

Freq - is the keyword that selects the appropriate frequency

All M2 parts internal k31, k250, k500, m1, m2, m4, m8, m16, m32  
20X2 internal k31, k250, k500, m1, m2, m4, m8, m16, m32 ,m64  
28X2, 40X2 internal k31, k250, k500, m1, m2, m4, m8, m16 external em16, em32, em40, em64
All default  

Superseded older parts:

08M, 14M, 20M internal m4, m8  
18A, 18M, 18X internal m4, m8  
28X1, 40X1 internal k31, k125, k250, k500, m1, m2, m4, m8 external em4, em8, em10, em16, em20
28X2-5V, 40X2-5V internal k31, k250, k500, m1, m2, m4, m8 external em16, em32, em40
28X2-3V, 40X2-3V internal k31, k250, k500, m1, m2, m4, m8, m16 external em16, em32, em40, em64
where k31 = 31kHz internal resonator
  m4 = 4MHz internal resonator etc.
  em16 = 16MHz external resonator etc.
Description:

Set the internal clock frequency for microcontrollers with internal resonator to 8MHz (m8) or some other value.

The default value on X2 parts is 8MHz internal. The default value on all other parts is 4MHz internal. The default value can be restored by using 'setfreq default'

The setfreq command can be used to change the speed of operation of the microcontroller from 4MHz to 8MHz (or some other value). However note that this speed increase affects many commands, by, for instance, changing their properties (e.g. all pause commands are half the length at 8MHz).

Note that the X2 parts have an internal x4 PLL inside the chip. This multiplies the external resonator speed by 4. Therefore the external resonator value to be used is 1/4 of the desired final speed (ie in mode em40 use an external 10MHz resonator, for em16 use a 4MHz resonator).

The change occurs immediately. All programs default to m4 (4MHz) if a setfreq command is not used (default is increased to m8, 8MHz on X2 parts).

Note that the Programming Editor only supports certain frequencies for new program downloads. If your chip is running at a different frequency the M2, X1 and X2 parts will automatically switch back to internal 4MHz /8MHz default speed to complete the download.

On M2 'multi-tasking' programs the setfreq command may not be used, as the oscillator speed is under control of the PICAXE firmware for task processing. The internal resonator frequencies are factory preset to the most accurate settings. However advanced users may use the calibfreq command to adjust these factory preset settings. Some commands such as readtemp will only work at 4MHz. In these cases change back to 4MHz temporarily to operate these commands (on M2, X1 and X2 parts this is automatic). Note that a temporary change in frequency (either programmed or automatic) will have a direct effect on background frequency dependant tasks such as pwmout / hpwm.

Applies To:
All (except 08, 18, 18A, 28, 28A, 28X, 40X)
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Changing operating speeds

This program demonstrate selecting 32MHz operation using an external crystal, switching to internal 4MHz operation, and then returning to 32MHz operation using the external crystal again.

Code Example:
	setfreq em32	; setfreq to external 32MHz
	pause 4000	; NB not 4 seconds as overclocked
	setfreq m4	; setfreq to 4MHz
	readtemp 1,b1	; do command at 4MHz
	setfreq em32	; set freq back to 32MHz
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