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4 cautions in using the timer carry ff – NEC PD17062 User Manual

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PD17062

12.4 CAUTIONS IN USING THE TIMER CARRY FF

The timer carry FF is used not only as a timer function but also as a reset sync signal at a CE reset.

A CE rest occurs when the timer carry FF set pulse rises after the CE pin goes from a low to a high.

Note the following points:

(1) The sum of the time used to update the timer and the time interval at which the BTM0CY flag is checked

must be less than the timer carry FF setting time interval.

(2) If a created program needs a timer that operates at constant intervals regardless of a CE reset once a power-

on reset occurs, the program must correct the timer at each CE reset.

(3) A check of the BTM0CY flag takes precedence over a reset sync signal for a CE reset. If both occur at the

same time, a CE reset is delayed one cycle.

Sections 12.4.1 to 12.4.3 detail the above topics.