Tech Support > Computer Hardware > Microprocessors > TMS470's HET module - looking for an opinion
TMS470's HET module - looking for an opinion
Posted by void on April 18th, 2006


Hello

I'm looking for someone who has some experience in using the TMS470's
HET module.
I've read the docs and analyzed examples for the HET,
but after spending almost entire day... uhm,...

I need to drive 8 injectors using waveforms like this:



<-time A-> <- time B (PWM, 50%) ->
__________ _ _ _ _ _ _ _ _ _ _ _
____| |_| |_| |_| |_| |_| |_| |_| |_| |_| |_| |_| |_________

time A - range 0-5ms, 0.01ms resolution
time B - range 0-60ms, 0.01ms resolution, pwm carrier period about 100us


After an event occurs, I set up parameters of a waveform (time A and
time B), start it and go to do some other things.
Very simple, but the problem is... I need 8 such outputs.
I'm not sure if a device like TMS470R1A256 running at 48MHz would handle
this using 1 HET. It looks like it would be easy cake for the HET to
generate 8 pwms, but I have some doubts about starting and setting this
A and B times independently for every one of 8 'channels'...
The HET seems to have only 3 registers for parameters, does that mean
the solution would require on-the-fly HET program changes done by the
CPU?

I would really appreciate an opinion of someone who has used the HET.
Although any suggestion will be a great help.
Maybe some other 32bit mcu (for an automotive application)?

Thanks
Kuba


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