HT82K70E-L datasheet(21/59 Pages) HOLTEK

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HT82K70E-L/HT82K70A-L/HT82K76E-L

Rev. 1.20

February 1, 2011

that setting the timer enable bit high to turn the timer on,

should only be executed after the timer mode bits have

been properly setup. Setting the timer enable bit high to-

gether with a mode bit modification, may lead to improper

timer operation if executed as a single timer control regis-

ter byte write instruction.

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 timer interrupt is 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

tobe 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 tmr0int

; jump here when Timer/Event Counter 0 overflows

org 0ch

; Timer/Event Counter 1 interrupt vector

jmp tmr1int

; jump here when Timer/Event Counter 1 overflows

org 20h

; main program

;internal Timer/Event Counter 0 interrupt routine

tmr0int:

; Timer/Event Counter 0 main program placed here

reti

;internal Timer/Event Counter 1 interrupt routine

tmr1int:

; Timer/Event Counter 1 main program placed here

reti

begin:

;setup Timer/Event Counter 0 registers

mov a,0e8h

; setup low byte preload value for Timer/Event Counter 0

mov tmr0l,a

; low byte must be setup before high byte

mov a,09bh

; setup high byte preload value for Timer/Event Counter 0

mov tmr0h,a

;

mov a,080h

; setup Timer control register TMR0C

mov tmr0c,a

; Timer/Event Counter 0 has no prescaler and clock source is fSYS/4

;setup Timer/Event Counter 1 registers

mov a,09bh

; setup low byte preload value for Timer/Event Counter 1

mov tmr1l,a

; low byte must be setup before high byte

mov a,0e8h

; setup high byte preload value for Timer/Event Counter 1

mov tmr1h,a

;

mov a,080h

; setup Timer control register TMR1C

mov tmr1c,a

; Timer/Event Counter 1 has no prescaler and clock source is fSYS/4

; setup interrupt register

mov a,00dh

; enable master interrupt and timer interrupts

mov intc,a

set tmr0c.4

; start Timer/Event Counter 0

- note mode bits must be previously setup

set tmr1c.4

; start Timer/Event Counter 1

- note mode bits must be previously setup

HT82K70E-L Datasheet(PDF) 21 Page - Holtek Semiconductor Inc

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