How to calculate CTU compare register value(MPC5744xp)

[xiemeijuan]

My work target:

At the middle point of FlexPWM0_B2  to trigger CTU to trigger the ADC commands.

Motc_Clk:

160Mhz

PWM setting: 

Centered aligned 

prescaler:PRESC_1

CTU setting:

prescaler:PRESC_4

Method1:  Set PWM0_B2 VAL0 output trigger to CTU 

Issues:      I found CTU trigger is not in the middle of FlexPWM0_B2 (No CTU TCR0V=0)

Question:  Why VAL0 output trigger is not in the middle of FlexPWM?

Method2: Set PWM0_B2 VAL4 output trigger to CTU 

Issues:

When I set VAL4 output trigger to CTU, I found the TCR0V needed to be varied with PWM period and dutycyle.

Question:

So how to set TCR0V according to PWM prescaler,PWM period and dutycyle and CTU prescaler? For example,PWM frequency 20Khz,50% duty cyle.

[PetrS · Accepted solution]

Hi,

Set the same prescaler for both the PWM and CTU’s TGS counters. TGS counter starts from TGSCRR up to TGSCCR and is reloaded at MRS. So you can set TGSCRR=0 and TGSCCR equal to PWM period. Then is VAL0 is used for MRS generation, and T0CR = 0 you should get T0 trigger generation at the time of VAL0 compare.

BR, Petr