PC87570 datasheet(108/168 Pages) NSC

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Multi-Function 16-Bit Timer (MFT16)

108

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14.3.5

Counter Clock Source Select

The clock source unit contains two clock source selectors

which allow you to independently select the clock source for

each of the two 16-bit counters from one of the following

sources:

• No clock, in which case the counter is stopped

• Prescaled system clock

• External Event count based on TB

• Pulse Accumulate mode based on TB

• Slow Speed Clock i.e., 32.768 KHz

14.4 TIMER/COUNTER AND ACTION UNIT

The timer/counter and action unit consists of two 16-bit

counters, TCNT1 and TCNT2, plus two 16-bit reload/cap-

ture registers, TCRA and TCRB. The timers are down

counters capable of triggering events on underflow detec-

tion (count from 0000h to FFFFh). In addition, it contains the

mode control logic which allows the timer to operate in any

of four operation modes described below.

Different interrupts can be triggered on certain conditions

and the functionality of the I/O pins change depending of the

mode of operation. Therefore the interrupt control and I/O

control are an integral part of the timer/counter unit.

14.4.1

Operation Modes

You can configure the MFT16 to operate in any one of four

modes, as summarized in Table 14-1 and described in this

section.

Table 14-1. Operation Modes

Mode

Description

Timer/Counter 1

(

TCNT1)

Reload/Capture A

(

TCRA)

Reload/Capture B

(

TCRB)

Timer/Counter 2

(

TCNT2)

PWM and system

timer or external

event counter

Counter for PWM

Auto Reload A =

PWM time I

Auto reload = PWM

time II

System Timer or

external event

counter

Dual input capture

and system timer

Capture A and B

time base

Capture counter 1

value on

TA event

Capture counter 1

value on

TB event

System Timer

Dual independent

timer

Time base for ﬁrst

timer

Reload register for

timer/counter I

Reload register for

timer/counter II

Time base for

second timer

Input capture and

timer

Time base for ﬁrst

timer

Reload register for

timer/counter I

Capture counter 1

value on

TB event

Capture B time

base

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