# 56803 PWM duty cycle sweep speed

Started by June 14, 2004
 Hi We are presently trying to use the DSP56F803 PWM (channel 4) as a simple independent PWM output. We are sweeping the output duty cycle from 0% to 100% and therefore, updating and reloading the PWM timer on every timeout interrupt of the PWM. When we then observe the PWM output on a scope, the rate at which the PWM duty cycle is changing, is taking much longer then we would expect (4 to 5 sec to go from 0 to 100 % duty cycle). We have also seen that the rate at which this output duty cycle can be changed is somehow tied to the configured base frequency of the PWM. Is this normal operation as per the 56803 implementation of the PWM functionality? Has anyone gotten the duty cycle to change faster? The prescaler and modulus are set for PWM freq = 4.32khz. We expected the duty cycle to change in microseconds or milliseconds, not seconds. Thanks Mike Kertesz
 Hi We are presently trying to use the DSP56F803 PWM (channel 4) as a simple independent PWM output. We are sweeping the output duty cycle from 0% to 100% and therefore, updating and reloading the PWM timer on every timeout interrupt of the PWM. When we then observe the PWM output on a scope, the rate at which the PWM duty cycle is changing, is taking much longer then we would expect (4 to 5 sec to go from 0 to 100 % duty cycle). We have also seen that the rate at which this output duty cycle can be changed is somehow tied to the configured base frequency of the PWM. Is this normal operation as per the 56803 implementation of the PWM functionality? Has anyone gotten the duty cycle to change faster? The prescaler and modulus are set for PWM freq = 4.32khz. We expected the duty cycle to change in microseconds or milliseconds, not seconds. Thanks Mike Kertesz
 Hello We are presently trying to use the DSP56F803 PWM (channel 4) as a simple independent PWM output. We are sweeping the output duty cycle from 0% to 100% and therefore, updating and reloading the PWM timer on every timeout interrupt of the PWM. When we then observe the PWM output on a scope, the rate at which the PWM duty cycle is changing, is taking much longer then we would expect (4 to 5 sec to go from 0 to 100 % duty cycle). We have also seen that the rate at which this output duty cycle can be changed is somehow tied to the configured base frequency of the PWM. Is this normal operation as per the 56803 implementation of the PWM functionality? Has anyone gotten the duty cycle to change faster? The prescaler and modulus are set for PWM freq = 4.32khz. We expected the duty cycle to change in microseconds or milliseconds, not seconds. Thanks Mike Kertesz