HT45F23 datasheet(69/152 Pages) HOLTEK

69 / 152 page

When the Timer/Event counter overflows, its corresponding interrupt request flag in the interrupt

control register will be set. If the timer interrupt is enabled this will in turn generate an interrupt signal.

However irrespective 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 condition. 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 external 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 request 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

interrupts 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

org 0ch

; Timer/Event Counter 0 interrupt vector

jmp tmrint

; jump here when the Timer/Event Counter 0 overflows

org 20h

; main program

;internal Timer/Event Counter 0 interrupt routine

tmrint:

; Timer/Event Counter 0 main program placed here

reti:

begin:

;setup Timer 0 registers

mov a,09bh

; setup Timer 0 preload value

mov tmr0,a;

mov a,081h

; setup Timer 0 control register

mov tmr0c,a

; timer mode and prescaler set to /2

; setup interrupt register

mov a,009h

; enable master interrupt and timer interrupt

mov intc0,a

set tmr0c.4

; start Timer/Event Counter 0 - note mode bits must be previously

; setup

HT45F23/HT45F43

8-Bit Flash MCU with Op Amps & Comparators

Rev. 1.20

September 15, 2011

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