M32C83T datasheet(166/527 Pages) RENESAS

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Page 143

14. Timer (Timer A)

)

(

14.1.2 Event Counter Mode

In event counter mode, the timer counts how many external signals are applied or how many times

another timer overflows and underflows. The timers A2, A3 and A4 can count externally generated two-

phase signals. Table 14.4 lists specifications in event counter mode (when not handling a two-phase

pulse signal). Table 14.5 lists specifications in event counter mode (when handling a two-phase pulse

signal with the timer A2, A3 and A4). Figure 14.9 shows the TAiMR (i=0 to 4) register in event counter

mode.

Table 14.4 Specifications in Event Counter Mode (when not processing two-phase pulse signal)

Item

Specification

Count Source

• External signal applied to the TAiIN pin (i = 0 to 4) (valid edge can be selected by

program)

• Timer B2 overflow or underflow signal, timer Aj overflow or underflow signal (j=i-1,

except j=4 if i=0) and timer Ak overflow or underflow signal (k=i+1, except k=0 if i=4)

Counting Operation

• External signal and program can determine whether the timer increments or decre-

ments the counter

• When the timer counter underflows or overflows, the content of the reload register is

reloaded into the count register and counting resumes. When the free-running count

function is selected, the timer counter continues running without reloading.

Divide Ratio

• 1/(FFFF16 - n + 1) for counter increment

• 1/(n + 1) for counter decrement

n : setting value of the TAi register 000016 to FFFF16

Counter Start Condition

The TAiS bit in the TABSR register is set to "1" (starts counting)

Counter Stop Condition

The TAiS bit is set to "0" (stops counting)

Interrupt Request Generation Timing The timer counter overflows or underflows

TAiIN Pin Function

Programmable I/O port or count source input

TAiOUT Pin Function

Programmable I/O port, pulse output or input selecting a counter increment or decrement

Read from Timer

The TAi register indicates counter value

Write to Timer

• When the timer counter stops,

the value written to the TAi register is also written to both reload register and counter

• While counting,

the value written to the TAi register is written to the reload register

(It is transferred to the counter at the next reload timing)

Selectable Function

• Free-running count function

Content of the reload register is not reloaded even if the timer counter overflows or

underflows

• Pulse output function

The polarity of the TAiOUT pin is inversed whenever the timer counter overflows or

underflows

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