TM4C123GH6PM: QEI Clocking Frequency

Pranjal Shrivastava

Prodigy 210 points

Part Number: TM4C123GH6PM

I m writing a driver for QEI peripheral on the TM4C123GH6PM .

The position part works fine , however there are issues while using the QEI velocity of the peripheral.

I DONT KNOW WHAT IS THE FREQUENCY MY QEI TIMER IS COUNTING AT??

MY F_CPU is 50MHz , that is sure, and I haven't made any change (it's all default).

Can you guys please tell me what frequency does the peripheral run on, I m not getting it by the clock tree in the manual .

I wish to use the formula to calculate RPM given in the manual, accurately to do that I NEED THE FREQUENCY.

Thanks!

over 6 years ago

0 Bob Crosby over 6 years ago

TI__Guru 72500 points

It runs at system clock frequency, in your case 50MHz.

0 Pranjal Shrivastava over 6 years ago in reply to Bob Crosby

Prodigy 210 points

But while reading the value of RCC register, shows that SYSDIV value is such that it is /4 , so isn't my peripheral clock rate 12.5MHz (50/4) ??

Doesn't TM4C have programmable clock divisors for peripherals like others (LPC1768) etc??

0 Bob Crosby over 6 years ago in reply to Pranjal Shrivastava

TI__Guru 72500 points

The SYSDIV value of the RCC register is used to generate the system clock. If your CPU is running at 50MHz, (SysCtlClockGet() returns 50,000,000) then the PLL output is 200MHz and the SYSDIV makes the system clock 50MHz. The QEI is clocked at system clock frequency.

Pranjal Shrivastava said:
Doesn't TM4C have programmable clock divisors for peripherals like others (LPC1768) etc??

Only in the peripherals that need them such as the ADC.

0 Pranjal Shrivastava over 6 years ago in reply to Bob Crosby

Prodigy 210 points

Okay , Thanks :D

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TM4C123GH6PM: QEI Clocking Frequency