hi all,

can you help me to generate a 0.8 khz pulse with SFB49. How can i change the pulse / interpulse ratio.

thanks in advance.

hi,

have you seen the manual: 

SIMATIC S7-300 CPU 31xC Technological Functions

In chapter 5.7 is a detailed description of PWM with SFB49.

hope this helps,

regards,

hi there,

i have the manual. but unfortunately i could not find any parameter or formula to be able to calculate the frequency. i can set the period time but i don't know how to set pulse/interpulse ratio in the period. 

hi Phuggy,

Over Job ID 01 hex you are writing the period-lenght.

whit the parameter OUTP_VAL you are specifying the output value (from 0..1000 or from 0..27648). That Value decribes the pulse duration/interpuls period-ratio.

hope this helps,

regards,

thank you very much mopS04

i want to ask you something to be sure about the parameters.

i think the period length value that we set in the HW config is automatically writed on the JOB ID 01. İs that true or do i have to write the period length value here again?

secondly, if i select the ppm and enter the value 500 in the OUTP_VAL, it means 50 percent of the period is high level. and writing 800 is 80 percent of the period is high level in the same way.

i will be so glad if you answer.

Phuggy Sweetrock

thank you very much mopS04

i want to ask you something to be sure about the parameters.

i think the period length value that we set in the HW config is automatically writed on the JOB ID 01. İs that true or do i have to write the period length value here again?

secondly, if i select the ppm and enter the value 500 in the OUTP_VAL, it means 50 percent of the period is high level. and writing 800 is 80 percent of the period is high level in the same way.

i will be so glad if you answer.

 hi Phuggy,

yes, you can set the period length in HW, but you also can controll it via SFB49. If it is already set in HW-Config you don´t have to do it anymore. To be sure you can read it out with JOB_ID 81 hex.

If you have selected the output format per mil you are right with 500 for 50% and 800 for 80% in OUTP_VAL. When your Output format is set to S7 analog value the value range from 0..27648 is for 0..100% 

hope this helps, 

regards,

thank you very very much mopS04. 

that was really helpful. have a great day!