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TIMER A

7721 Group User’s Manual

8–26

8.4 Event counter mode

(2)

Two-phase pulse signal processing function

The two-phase pulse signal processing function is selected by setting the two-phase pulse signal

processing select bits (bits 5 to 7 at address 4416) to “1.” (Refer to “Figure 8.4.5.”) Figure 8.4.6

shows the timer Aj mode registers when the two-phase pulse signal processing function is selected.

For timers with the two-phase pulse signal processing function selected, the timer counts two kinds

of pulses of which phases differ by 90 degrees. There are two types of the two-phase pulse signal

processing: normal processing and quadruple processing. In Timers A2 and A3, normal processing

is performed; in timer A4, quadruple processing is performed.

For some bits of the port P5 direction register correspond to pins used for two-phase pulse input, set

these bits for the input mode.

Fig. 8.4.6 Timer Aj mode registers when two-phase pulse signal processing function is selected

qNormal processing

Countup is performed at the rising edges input to the TAkIN pin when the phase has the relationship

that the TAkIN pin’s input signal level goes from “L” to “H” while the TAkOUT (k = 2 and 3) pin’s input

signal is at “H” level.

Countdown is performed at the falling edges input to the TAkIN pin when the phase has the

relationship that the TAkIN pin’s input signal level goes from “H” to “L” while the TAkOUT pin’s input

signal is at “H” level. (Refer to “Figure 8.4.7.”)

Fig. 8.4.7 Normal processing

Timer A2 mode register (Address 5816)

Timer A3 mode register (Address 5916)

Timer A4 mode register (Address 5A16)

! : It may be either “0” or “1.”

TAkOUT

TAkIN

(k=2, 3)

count

–1

Counted

down

Counted

down

Counted

down

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