LPC54xx The maximum frequency for the SCTimer/PWM clock is 100 MHz ??

[ZhaiYF]

Question 1、
In the figure  "The maximum frequency for the SCTimer/PWM clock is 100 MHz."
Is it only applicable for clock after SCTCLKSEL ?

Question 2、
If set CLKMODE=0 in SCTimer/PWM configuration register。Is there maximum frequency
limit for system clock ?

[ZhangJennie]

HI ZhaiYF 

The Maximum freq for SCT is 100Mhz. any input freq. beyond this value is an invalided input and will have un-guaranteed behavior. also , the 100Mhz limit is mainly com from pad limitation. not the SCT module itself

Have a nice day, 

Jun Zhang

[ZhaiYF]

HI Jun Zhang

Thanks.

Maybe I confused the SCTimer clock source and clock input. 

Now, SCTimer does not need any external clock input except the system clock. I want to Confirm whether the SCTimer module can work stably if the system clock is greater than 100MHz, such as 180MHz.

The MCU used is lpc54618.

[ZhangJennie · Accepted solution]

Hi ZhaiYF 

There are two type of input for SCT, the the 100MHz clock limitation is only valid for the clock source inputted from external pads (SCT_IN7), if you use system clock as the SCTimer/PWM clock source, the system clock frequency can be greater than 100MHz.

ZhangJennie_0-1640610687604.png

You can also see this "Remarks "  immediately below "Select a function clock using SCTCLKSEL (Section 7.5.41)."

ZhangJennie_1-1640610889410.png

Hope this helps,

Jun Zhang