UPD17708 datasheet(155/356 Pages) NEC

155 / 356 page

155

µPD17704, 17705, 17707, 17708, 17709

(2) Error when time interval to set BTM0CY flag is changed

The BTM0CK1 and BTM0CK0 flags set the time of the BTM0CY flag.

As described in 13.2.2, four types of timer time-setting pulses can be selected: 10 Hz, 20 Hz, 50 Hz, and

100 Hz.

At this time, these four pulses operate independently. If the timer time-setting pulse is changed by using

the BTM0CK1 and BTM0CK0 flags, an error occurs as described in the example below.

Example

; <1>

INTIFLG NOT BTM0CK1, NOT BTM0CK0 ; Sets BTM0CY flag setting pulse to 10 Hz

(100 ms)

Processing A

; <2>

INITFLG BTM0CK1, NOT BTM0CK0

; Sets BTM0CY flag setting pulse to 50 Hz

(20 ms)

Processing A

; <3>

INITFLG NOT BTM0CK1, NOT BTM0CK0 ; Sets BTM0CY flag setting pulse to 10 Hz

(100 ms)

At this time, the BTM0CY flag setting pulse is changed as shown in Figure 13-6.

Figure 13-6. Changing BTM0CY Flag Setting Pulse

As shown in Figure 13-6, if the BTM0CY flag setting time is changed and the new pulse falls, the BTM0CY

flag retains the previous status (<2> in the figure). If the new pulse rises, however, the BTM0CY flag

is set to “1” (<3> in the figure).

Although changing the pulse setting between 10 Hz (100 ms) and 50 Hz (20 ms) is described in this

example, the same applies to changing the pulse in respect to 20 Hz (50 ms) and 100 Hz (10 ms).

Internal pulse

10 HZ

Internal pulse

50 HZ

BTM0CY flag

setting pulse

SKT1 BTM0CY

<2>

<3>

<1>

UPD17708 Datasheet(PDF) 155 Page - NEC