Hi all. I have an application that uses Timer A and B CCR's on a MSP430F437 to generate a programmable pulse train. Generally the timers are programmed and set in motion until the user request a stop. However several of the modes demand a very short burst rate of a high frequency pulse. For example 500Khz 0.5uS pulse for 20uS, repeating at 1kHz.

Longer burst times are achieved using interrupt but these short ones are done by simply activating the timers and then performing a hard delay in code and stopping them. After each stoppage the timer registers are completely reset.

The problem comes when, depending on the delay between start and stop, the first pulse of the train is longer (1.5uS). This does NOT happen on the very first set of pulses but consistently on every subsequent one leading me to think it is some hardware no being properly reset - but I can see nothing else to reset!

The MSP is running at 8Mhz so we are dealing with little counts of 3 for 0.5uS. I also note that the shut-down of the timers is completely arbitrary and they could be shut down while a CCR output is active. All I can think is that this then comes back though some sort of hardware glitch as additional pulse width on the next pulse?

Very confused. (also sorry for length)

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