SEC2410 datasheet(79/283 Pages) MICROCHIP

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DS00001587C-page 79

SEC2410/SEC4410

11.6

Operating Modes

11.6.1

TIMER MODE

The Timer mode of the SEC2410/SEC4410 is used to generate periodic interrupts to the EC. When operating in this

mode the timer always counts down based on one of the internally generated clock sources. The Timer mode is selected

by setting the Timer Mode Select bits in the Timer Control Register. See Section 11.8.1, "Timer x Control Register," on

page 86.

The period between timer interrupts and the width of the output pulse is determined by the speed of the clock source,

the clock divide ratio and the value programmed into the Timer Reload Register. The timer clock source and clock rate

are selected using the Clock Source Select bits (TCLK) in the Timer x Clock and Event Control Register. See Section

11.8.2, "Timer x Clock and Event Control Register," on page 87.

11.6.1.1

Timer Mode Underflow

The SEC2410/SEC4410 timers operating in Timer mode can underflow in two different ways. One method, the Reload

mode shown in Figure 11-2, is to reload the value programmed into the Reload register and continue counting from this

value. The second method, Free Running mode Figure 11-3, is to set the timer to FFFFh and continue counting from

this value. The underflow behavior is controlled by the RLOAD bit in the Timer Control Register.

TABLE 11-3:

TIMER 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

Down Counter

Reload Operation

When the timer underflows:

RLOAD = 1, timer reloads from Timer Reload Reg

RLOAD = 0, timer rolls over to FFFFh.

Count Start Condition

UPDN = 0 (timer only mode): ENABLE = 1

UPDN = 1 (timer gate mode): ENABLE = 1 & TIN = 1;

Count Stop Condition

UPDN = 0: ENABLE = 0;

UPDN = 1: (ENABLE= 0 | TIN = 0)

Interrupt Request Generation

Timing

When timer underflows from 0000h to reload value (as determined by RLOAD) an

interrupt is generated.

TINx Pin Function

Provides timer gate function

TOUTx Pin Function

TOUT toggles each time the timer underflows (if enabled).

Read From Timer

Current count value can be read by reading the Timer Count Register

Write to Preload Register

After the firmware writes to the Timer Reload Register asserting the RESET loads

the timer with the new value programmed in the Timer Reload Register.

Note: If the firmware does not assert RESET, the timer will automatically load the

Timer Reload Register value when the timer underflows. When the timer is

running, values written to the Timer Reload Register are written to the timer

counter when the timer underflows. The assertion of Reset also copies the Timer

Reload Register into the timer counter.

Selectable Functions



Reload timer on underflow with programmed Preload value (Basic Timer)



Reload timer with FFFFh in Free Running Mode (Free-running Timer)



Timer can be started and stopped by the TINx input pin (Gate Function)



The TOUTx pin changes polarity each time the timer underflows (Pulse Output

Function)

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