HT46R01 datasheet(23/60 Pages) HOLTEK

23 / 60 page

HT46R01/HT46R02/HT46R03

Rev. 1.00

September 21, 2007

the timer registers before the timer is switched on; this is

because after power-on the initial values of the timer reg-

isters are unknown. After the timer has been initialised

the timer can be turned on and off by controlling the en-

able bit in the timer control register.

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

²HALT² instruction to enter the Power Down Mode.

Timer Program Example

The following example program section is based on the

HT46R02 and HT46R03 devices, which contains two in-

ternal 8-bit Timer/Event Counters. The program 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 respective 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 Counters to be in the timer mode, which

uses the internal system clock as their clock source.

org 04h

; external interrupt vector

reti

org 08h

; Timer Counter 0 interrupt vector

jmp tmr0int ; jump here when Timer 0 overflows

org 0ch

; Timer Counter 1 interrupt vector

jmp tmr1int ; jump here when Timer 1 overflows

org 20h

; main program

;internal Timer 0 interrupt routine

tmr0int:

; Timer 0 main program placed here

reti

;internal Timer 1 interrupt routine

tmr1int:

;Timer 1 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 Timer 1 registers

clr tmr1

; clear timer register to give maximum count value

mov a,080h

; setup Timer 1 control register

mov tmr1c,a ; timer mode - Timer 1 has no prescaler

;setup interrupt register

mov a,00dh

; enable master interrupt and both timer

; interrupts

mov intc0,a

set tmr0c.4 ; start Timer 0

set tmr1c.4 ; start Timer 1

HT46R01 Datasheet(PDF) 23 Page - Holtek Semiconductor Inc

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