SEC2410 datasheet(84/283 Pages) MICROCHIP

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SEC2410/SEC4410

DS00001587C-page 84

 2013 - 2014 Microchip Technology Inc.

11.6.4

MEASUREMENT MODE

The Measurement mode is used to measure the pulse width or period of an external signal. An interrupt to the EC is

generated after each measurement or if the timer overflows and no measurement occurred. The timer measures the

pulse width or period by counting the number of clock between edges on the TINx pin. The timer always stars counting

at zero and counts up to 0xFFFF. The accuracy of the measurement depends on the speed of the clock being used. The

speed of the clock also determines the maximum pulse width or period that can be detected.

11.6.4.1

Pulse Width Measurements

The timers measure pulse width by counting the number of timer clocks since the last rising or falling edge of the TINx

input. To measure the pulse width of a signal on the TINx pin, bits in the Clock and Event Control Register, must be set

to start counting on rising and falling edges. The timer starts measuring on the next edge (rising or falling) on the TINx

pin after the ENABLE bit is set. The Reload register stores the result of the last measurement taken. If the timer over-

flows, 0x0000 is written to the Reload register and the ENABLE bit is cleared stopping the timer. Figure 11-10 shows

the timer behavior when measuring pulse widths.

The timer will not assert an interrupt in Pulse Measurement mode until the timer detects both a rising and a falling edge.

TABLE 11-6:

MEASUREMENT MODE OPERATIONAL SUMMARY

Item

Description

Timer Clock Frequencies

This mode supports all the programmable frequencies listed in Table 11-10, “Timer

Clock Frequencies,” on page 88

Filter Clock Frequencies

This mode supports all the programmable frequencies listed in Table 11-10, “Timer

Clock Frequencies,” on page 88

Count Operation

• Up Count

• At measurement pulse's effective edge, the count value is transferred to the Timer

Reload Register and the timer is loaded with 0000h and continues counting.

Count Start Condition

• Timer enable is set (ENABLE = 1)

Count Stop Condition

• Timer is reset (RESET = 1)

• Timer overflows

• Timer enable is cleared (ENABLE = 0)

Interrupt Request

Generation Timing

• When timer overflows

• When a measurement pulse’s effective edge is input. (An interrupt is not gener-

ated on the first effective edge after the timer is started.)

TINx Pin Function

Programmable Input port or Measurement input

Read From Timer

When the Timer x Reload Register is read it indicates the measurement result from

the last measurement made. The Timer x Reload Register reads 0000h if the timer

overflows before a measurement is made.

Write to Timer

Timer x Reload Register is Read-Only in Measurement mode

FIGURE 11-10:

PULSE WIDTH MEASUREMENT

Timer Value

TIN

Timer Clock

0x000

Timer Reload

Timer Enable Bit

0x000

0xFFF

0x000

Timer Interrupt

0x000

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