UPD17015GS datasheet(45/120 Pages) NEC

45 / 120 page

µPD17015

As shown in Fig. 10-4, when the BTM0CY and BTM1CY flags are detected at 2 , the timer is updated because

the flag is “1”. When the flag is detected at 3 , because it is “0”, the timer is not updated until it is detected again

. Therefore, the timer is incremented by tCHECK3.

10.2.5

Cautions for Using Basic Timers 0 and 1

(1) BTM0CY and BTM1CY flags detection time interval

As described in Section 10.2.4, keep the BTM0CY and BTM1CY flags detection time interval shorter than the

BTM0CY and BTM1CY flags set time interval.

Otherwise, the BTM0CY and BTM1CY flags cannot be set if the time required for process B is longer than the

BTM0CY and BTM1CY flags set time interval, as shown in Fig. 10-5.

Fig. 10-5 Detection of the BTM0CY and BTM1CY Flags

(2) Sum of the timer update process time and the BTM0CY and BTM1CY flags detection time interval

As explained in (1), the BTM0CY and BTM1CY flags detection time interval must be kept shorter than the BTM0CY

and BTM1CY flags set time interval.

Even when the BTM0CY and BTM1CY flags detection time interval is short, however, if the timer update process

time is long, a CE reset may prevent a normal timer update process.

The following conditions must therefore be satisfied.

tCHECK + tTIMER < tSET

where

tCHECK : BTM0CY and BTM1CY flags detection time interval

tTIMER : Timer update process time

tSET

: BTM0CY and BTM1CY flags set time interval

The coding that meets these conditions is given below.

BTM0CY flag

set pulse

BTM1CY flag

set pulse

BTM1CY flag

BTM0CY flag

SKT1

BTM0CY

SKT1

BTM1CY

SKT1

BTM0CY

SKT1

BTM1CY

SKT1

BTM0CY

SKT1

BTM1CY

Process A

Process B

Because the time required for process B is long after

the BTM0CY and BTM1CY flags, which is set to "1" at

, is detected, the BTM0CY and BTM1CY flags,

which is set to "1" at

, cannot be detected.

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