HT95R35 datasheet(25/73 Pages) HOLTEK

25 / 73 page

HT95R35

Rev. 1.00

October 7, 2009

When the Timer/Event counter overflows, its corre-

sponding interrupt request flag in the interrupt control

will in turn generate an interrupt signal. However irre-

spective of whether the interrupts are enabled or not, a

Timer/Event counter overflow will also generate a

wake-up signal if the device is in a Power-down condi-

tion. This situation may occur if the Timer/Event Counter

is in the Event Counting Mode and if the external signal

continues to change state. In such a case, the

Timer/Event Counter will continue to count these exter-

nal events and if an overflow occurs the device will be

woken up from its Power-down condition. To prevent

such a wake-up from occurring, the timer interrupt re-

quest flag should first be set high before issuing the

HALT instruction to enter the Power Down Mode.

Timer Program Example

This program example shows how the Timer/Event

Counter registers are setup, along with how the inter-

rupts are enabled and managed. Note how the

Timer/Event Counter is turned on, by setting bit 4 of the

Timer Control Register. The Timer/Event Counter can

be turned off in a similar way by clearing the same bit.

This example program sets the Timer/Event Counter to

be in the timer mode, which uses the internal system

clock as the clock source.

Org

04h

; external interrupt vector

reti

Org

08h

; Timer/Event Counter 0 interrupt vector

jmp tmr0nt

; jump here when Timer 0 overflows

org 20h

; main program

;internal Timer/Event Counter interrupt routine

tmr0nt:

; Timer/Event Counter main program placed here

reti

begin:

;setup Timer registers

mov a,01fh

; setup preload value

- timer counts from this value to FFFFH

mov tmr01,a

mov a,09bh

mov tmr0h,a

mov a,080h

; setup Timer control register

mov tmr0c,a

; timer mode

; setup interrupt register

mov a,005h

; enable master interrupt and timer interrupt

mov intc0,a

set tmrc0.4

; start Timer

- note mode bits must be previously setup

HT95R35 Datasheet(PDF) 25 Page - Holtek Semiconductor Inc

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