Please help me understand Timer.. some documentation links...

[pIx]

I am new to Freescale microcontrollers and I managed the Timer to work and its interrupting. But inorder to do more complicated things with it that I intend on doing, I need to understand what and how it works. Kindly answer a few question I have or please provide me a link to some documentation that gives a somewhat detailed description of the process.

1. What is a PulseAccumulator and what is it used for?

2. In MSP430 microcontrollers I worked on, the documentation clearly explained its three counter modes: Up Counter, Down Counter and UP-Down counter. I know for sure HCS12 has these and probably much more, but where can I get some clearly wriiten info on how it works(I went through all the relevent datasheets on Freescale website without luck)

Thanks a million,
~Sujith

[DanielM]

ad 1) The pulse accumulator was originally created for ABS functionality (counting pulses comming from the sensors in individual wheels tracking their speed of rotation). This was some 10 years ago, the pulse accumulator is no longer used for the purpose in modern vehicles. However Freescale left it in the ECT module just for backwards compatibility so you will still find it on the newest members of the S12/X/E family today. What you use it for is up to you...

ad 2) no, the standard TIM and ECT modules are very simple and are not capable of these advanced counting modes. The both have only one counter (if you ignore the pulse accumulator add-on for the moment) which counts up. No options.

The best reference out there is the datasheet - look at the ECT or Timer sections. It is not the best manual on earth, but all the details are in there.

Daniel

[J2MEJediMaster]

Try going to the FAQ section of the Web site and searching for application note 2724 (try "HC12 PIT" for your search string). The doucment is titled "Using the HCS12X PIT as a 24-Bit Elapsed Timer" which should answer some of your questions. I've attached the file in question to help.

---Tom

http://www.freescale.com/files/microcontrollers/doc/app_note/AN2724.pdf

Message Edited by t.dowe on 2009-09-11 02:58 PM