Die PWM-Frequenz hat bei der normalen Steuerung von Motoren eine untergeordnete Rolle. Sie wird bestimmt durch den Teiler (Prescaler) und die Auflösung des Timers.
Dazu musst du unbedingt das Datenblatt des Mega8 heranziehen (die Register sind bei den Megas aber fast identisch).

Vielleicht sollten wir doch noch einen Artikel über PWM bei den Megas schreiben. Leide rfehlt mir ein wenig die Zeit zu, aber vielleicht hat jemand anders Lust.

Ich kopiere mir als Erinnerung gerne Bitbeschreibungen der Registe rin den Sourcecode, dann wird´s übersichtlicher.
Zum Beispiel so:

Code:
'PWM Frequenz Initialisieren
Tccr1a = &B10100010                                         '9 Bit PWM
' Bit 7/6 =  00  COM1A1/COM1A0  Pin OC1A nicht mit T/C1 verbunden
' Bit 7/6 =  01  COM1A1/COM1A0  Pin OC1A nicht mit T/C1 verbunden (wenn WGM13=0)
' Bit 7/6 =  10  COM1A1/COM1A0  bei Übereinstimmung OC1A LO beim Aufwärtszählen und Hi beim Abwärtszählen
' Bit 7/6 =  11  COM1A1/COM1A0  bei Übereinstimmung OC1A Hi beim Aufwärtszählen und Lo beim Abwärtszählen
' Bit 5/4 =  00  COM1B1/COM1B0  Pin OC1B nicht mit T/C1 verbunden
' Bit 5/4 =  01  COM1B1/COM1B0  Pin OC1B nicht mit T/C1 verbunden (wenn WGM13=0)
' Bit 5/4 =  10  COM1B1/COM1B0  bei Übereinstimmung OC1B LO beim Aufwärtszählen und Hi beim Abwärtszählen
' Bit 5/4 =  11  COM1B1/COM1B0  bei Übereinstimmung OC1B Hi beim Aufwärtszählen und Lo beim Abwärtszählen
' Bit 3/2 =      FOC1A/FOC1B    Neue Mega Bits - Bedeutung?
' Bit 1/0 =  00  WGM11/WGM10    PWM nicht aktiv
' Bit 1/0 =  01  WGM11/WGM10    8  Bit PWM
' Bit 1/0 =  10  WGM11/WGM10    9  Bit PWM
' Bit 1/0 =  11  WGM11/WGM10    10 Bit PWM

Tccr1b = &B10000001
' Bit 7   =    1    INCNC1  Noise Channel
' Bit 6   =    0    ICES1   Fallende Flanke
' Bit 5   =         WGM13
' Bit 4   =         WGM12
' Bit 2/1/0 =  000  CS12/CS11/CS10  Stop Timer/Counter 1
' Bit 2/1/0 =  001  CS12/CS11/CS10  Voller Takt
' Bit 2/1/0 =  010  CS12/CS11/CS10  Takt/8
' Bit 2/1/0 =  011  CS12/CS11/CS10  Takt/64
' Bit 2/1/0 =  100  CS12/CS11/CS10  Takt/256
' Bit 2/1/0 =  101  CS12/CS11/CS10  Takt/1024
' Bit 2/1/0 =  110  CS12/CS11/CS10  Externer Takt an Pin T1, fallende Flanke
' Bit 2/1/0 =  111  CS12/CS11/CS10  Externer Takt an Pin T1, steigende Flanke
In der Help-Datei von Bascom findet man schon was, du mußt nach Timer suchen, dann findest du das:

Code:
Action
Configure TIMER1.
 
 
Syntax
CONFIG  TIMER1 = COUNTER | TIMER | PWM , 
EDGE=RISING | FALLING ,   PRESCALE= 1|8|64|256|1024 , 
NOISE CANCEL=0 |1,  CAPTURE EDGE = RISING | FALLING , 
CLEAR TIMER = 1|0, 
COMPARE A = CLEAR | SET | TOGGLE I DISCONNECT  , 
COMPARE B = CLEAR | SET | TOGGLE I DISCONNECT  , 
PWM = 8 | 9  10 , 
COMPARE A PWM = CLEAR UP| CLEAR DOWN | DISCONNECT 

COMPARE B PWM = CLEAR UP| CLEAR DOWN | DISCONNECT 


Remarks
The TIMER1 is a 16 bit counter. See the hardware description of TIMER1.
It depends on the chip if COMPARE B is available or not.


The syntax shown above must be on one line. Not all the options need to be selected.

Here is the effect of the various options.

EDGE	You can select whether the TIMER will count on the falling or rising edge. Only for COUNTER mode.
CAPTURE EDGE	You can choose to capture the TIMER registers to the INPUT CAPTURE registers
With the CAPTURE EDGE = FALLING/RISING, you can specify to capture on the falling or rising edge of pin ICP
NOISE CANCELING	To allow noise canceling you can provide a value of 1.
PRESCALE	The TIMER is connected to the system clock in this case. You can select the division of the system clock with this parameter.
Valid values are 1 , 8, 64, 256 or 1024
The TIMER1 also has two compare registers A and B
When the timer value matches a compare register, an action can be performed

COMPARE A	The action can be:
SET will set the OC1X pin
CLEAR will clear the OC1X pin
TOGGLE will toggle the OC1X pin
DISCONNECT will disconnect the TIMER from output pin OC1X
And the TIMER can be used in PWM mode
You have the choice between 8, 9 or 10 bit PWM mode
Also you can specify if the counter must count UP or down after a match
to the compare registers
Note that there are two compare registers A and B


PWM	Can be 8, 9 or 10.
COMPARE A PWM	PWM compare mode. Can be CLEAR UP or CLEAR DOWN
Using COMPARE A, COMPARE B, COMPARE A PWM or COMPARE B PWM will set the corresponding pin for output. When this is not wanted you can use the alternative NO_OUTPUT version that will not alter the output pin.
For example : COMPARE A NO_OUTPUT , COMPARE A PWM NO_OUTPUT

Example
'-------------------------------------------------------------------
'                       TIMER1.BAS  for the 8515
'-------------------------------------------------------------------

Dim W As Word

'The TIMER1 is a versatile 16 bit TIMER.
'This example shows how to configure the TIMER

'First like TIMER0 , it can be set to act as a TIMER or COUNTER
'Lets configure it as a TIMER that means that it will count and that
'the input is provided by the internal clock.
'The internal clock can be divided by 1,8,64,256 or 1024
Config Timer1 = Timer , Prescale = 1024


'You can read or write to the timer with the COUNTER1 or TIMER1 variable
W = Timer1
Timer1 = W


'To use it as a COUNTER, you can choose on which edge it is triggered
Config Timer1 = Counter , Edge = Falling, , Prescale = 1024
'Config Timer1 = Counter , Edge = Rising

'Also you can choose to capture the TIMER registers to the INPUT CAPTURE registers
'With the CAPTURE EDGE = , you can specify to capture on the falling or rising edge of pin ICP
Config Timer1 = Counter , Edge = Falling , Capture Edge = Falling , , Prescale = 1024
'Config Timer1 = Counter , Edge = Falling , Capture Edge = Rising

'To allow noise canceling you can also provide :
Config Timer1 = Counter , Edge = Falling , Capture Edge = Falling , Noise Cancel = 1, , Prescale = 1024

'to read the input capture register :
W = Capture1
'to write to the capture register :
Capture1 = W





'The TIMER also has two compare registers A and B
'When the timer value matches a compare register, an action can be performed
Config Timer1 = Counter , Edge = Falling , Compare A = Set , Compare B =
 Toggle, , Prescale = 1
'SET , will set the OC1X pin
'CLEAR, will clear the OC1X pin
'TOGGLE, will toggle the OC1X pin
'DISCONNECT, will disconnect the TIMER from output pin OC1X


'To read write the compare registers, you can use the COMPARE1A and COMPARE1B variables
Compare1a = W
W = Compare1a


'And the TIMER can be used in PWM mode
'You have the choice between 8,9 or 10 bit PWM mode
'Also you can specify if the counter must count UP or down after a match
'to the compare registers
'Note that there are two compare registers A and B
Config Timer1 = Pwm , Pwm = 8 , Compare A Pwm = Clear Up , Compare B Pwm = Clear Down

'to set the PWM registers, just assign a value to the compare A and B registers
Compare1a = 100
Compare1b = 200

'Or for better reading :
Pwm1a = 100
Pwm1b = 200

End
Bruachst du überhaupt PWM? Oder verwechselst du das mit dem normalen Timer der auch Frequenzen erzeugen kann?
Lade dir dazu mal das Programm hier runter:

https://www.roboternetz.de/phpBB2/dl...le&file_id=169

Ich glaub das könnte was für dich sein.

Gruß Frank