Using Timer0 and Timer1

Anthony Scarnici said:

I'm trying to setup Timer0 and Timer1 to run in my program. I do not want them to interrupt, but rather, I'd like timer0 to count up and only stop when I stop it, and I'd like to take the final value of timer0, work some math on the number, then use it to set the period of timer1. I found the reference in SPRUFB0D, but it's a bit confusing about how to go about setting this up... can anyone help me out?

You are not obligated to configure the CPU Timer 0 and CPU Timer 1 to generate interrupts.  There is a bit field that disables the interrupt generation upon the timer register counting down to 0.

You may want to consult some examples that are available on the TMS320F28335 Product Folder.  You didn't explicitly mention this part number, but based on the document you reference, I assume you are using the TMS320F28335.

C2833x/C2823x C/C++ Header Files and Peripheral Examples

I'm sorry,I forgot to refernce the processor - it is  the TMS320F28335 - and I have been through the product folder already. I could find nothing on timers in there. Here's where I'm at:

I figured out how to, and then disabled the interrupts already. But I am a bit confused about how to set up the timers. The code example shows:

ConfigCpuTimer(&CpuTimer0, 150, 1000000);

I have already gotten this far setting up timer1 and timer0:

CpuTimer0Regs.TCR.bit.TIE = 0;   // Disable Timer0 interrupt

CpuTimer1Regs.TCR.bit.TIE = 0;         // Disable Timer1 interrupt

CpuTimer0Regs.TCR.bit.FREE = 0;        // FREE bit - setting for timer0 to handle breakpoints in debug mode - free run = 0

CpuTimer1Regs.TCR.bit.FREE = 0;   // FREE bit - setting for timer1 to handle breakpoints in debug mode - free run = 0

CpuTimer0Regs.TCR.bit.SOFT = 0;   // SOFT bit - sets timer0 to halt after next decrement of TIMH:TIM (hard stop)

CpuTimer1Regs.TCR.bit.SOFT = 0;        // SOFT bit - sets timer1 to halt after next decrement of TIMH:TIM (hard stop)

CpuTimer0Regs.TPR.bit.PSC =            // not set yet...

CpuTimer0Regs.TCR.bit.TRB =1;          // Timer0 Reload Bit - when set, TIMH:TIM gets loaded with the value in PRDH:PRD and PSCH:PSC with TDDRH:TDDR

CpuTimer1Regs.TCR.bit.TRB =1;          // Timer0 Reload Bit - when set, TIMH:TIM gets loaded with the value in PRDH:PRD and PSCH:PSC with TDDRH:TDDR

EPwm1Regs.TBCTL.bit.CTRMODE = 0;   // count up and start

for setting the interrupt, but what about just setting the timer? What goes in place of the pointer? basically, I want to tell it to cound down from a certain number, I'll stop it periodically, save the value, and start it again. The prescaler is a little fuzzy to me. Could you please give a breif breakdown and an example of usig the timer0 without the interupts, as well as reading the remaining value after the timer is stopped by software? One example code snippet is not really enough information for a beginner with this particular processor! Thanks!!

Anyone??

In particular, I'm looking for  better explanation of how to load period values, and how to work with the prescalar and timer divide down registers.

Consider the timer as a 32 bit down-counter. When the counter reaches 0, the counter is reloaded with the period value. This duration will be (period * input CLK period).

Now if you want a longer period than (SYSCLK * 2^32 ~ 53 seconds) you can pre-scale the input clock using the 8-bit TDDR, which extends the period by another 8 bits, where PSC is your lsb. So the total time read from the counters will be ~3.8 hours. Reading the two separate counters in sync will be tricky though.

But if you don't care about the timer resolution you can consider the pre-scalar as just an integer divider of SYSCLK and use 32-bit TIM counter for rough timing.

If the timer is running (TCR.TSS == 0), reloading will be automatic - when the counter reaches zero. You have the option to reload the counter using TCR.TRB bit, set to 1 to reload 32 bit counter (TIM) with PRD and 8 bit pre-scalar (PSC) with TDD.

Simple steps to do to configure a timer:

  /*

  * Timer 2 - used as 32bit 80MHz clock down-counter.

  */

CpuTimer2Regs.TCR.bit.TSS = 1;         // 1 = Stop timer, 0 = Start/Restart Timer

CpuTimer2Regs.PRD.all =  0xFFFFFFFF;  // Initialize timer period to maximum

CpuTimer2Regs.TCR.bit.TRB = 1;         // 1 = reload timer now

CpuTimer2Regs.TCR.bit.TIE = 0;         // 0 = Disable/ 1 = Enable Timer Interrupt

CpuTimer2Regs.TCR.all = 0;             // TSS = 0 = Start/Restart Timer

Later in your code you read the counter (all 32 bits) by 

Uint32 l_nCountNow = CpuTimer2Regs.TIM.all;

Thanks J - that clears a bit of stuff up. Bear with my questions...

If I want the timer to count down to 0 at a 40 Hz rate, and I'm running at 150Mhz, I divide to get 150Mhz/40Hz = 3750000 = 0x00393870 and that would be my PRD.all value that I load correct? And if I don't want to scale it I can load all zero's into the prescalar and divide down registers? Is there a way to make the timer NOT reload and restart when it reaches 0? Or does that require interupt sequences? The rest, I think I've figured out...

Tony

I'm looking to follow a sine wave and see if it phase shifts so stopping the counter will enable me to find that (I have another timer running as well - complicated crap that I dreamed up in my office...lol)

But thanks for all the help!!!