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What is the function of CNTR switching when using the timer output mode?

Latest Updated:12/07/2004

Question:

(Timer)   What is the function of the CNTR polarity switching bit when using the timer in pulse output mode? [2004/12/07]

Answer:

The configuration of the CNTR polarity switching bit is shown in the following figure.
This bit determines the output start level when the toggle flip-flop is initialized, for example at the start of pulse output. Also, if this bit is rewritten during pulse output, output level will reverse.

Once toggle flip-flop is initialized, Q = 0 (output polarity "L") and Q = 1 (output polarity "H") are set.
Toggle flip-flop initialization is caused by writing to the timer latch in pulse output mode or by selecting modes other than pulse output mode.
If the timer count stops, the output level at that time will be retained.

(Ex.1) When CNTR polarity switching bit = 0 at toggle flip-flop initialization
1. Toggle flip-flop Q = 1 initiates pulse output from "H"
2. Toggle flip-flop reverses to Q = 0 due to timer underflow, and pulse output switches to "L" output.

(Ex.2) When CNTR polarity switching bit = 1 at toggle flip-flop initialization
1. Toggle flip-flop Q = 0 initiates pulse output from "L"
2. Pulse output switches to "H" output due to timer underflow.
3. If data is written to timer latch, toggle flip-flop will reset to Q = 0 and pulse output will switch to "L" output.

* "Timer latch" signifies the timer latch of the applicable timer (timer X latch or timer Y latch).
"CNTR polarity switching bit" signifies the output pin polarity switching bit of the applicable timer (CNTR0 active edge switch bit or CNTR1 active edge switch bit).

(#105186)

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