HT83F02 datasheet(24/64 Pages) HOLTEK

24 / 64 page

HT83F02

Rev. 1.20

November 19, 2010

Time Base

The Time Base function will generate a regular interrupt

signal synchronised to the system clock which can be

used by the application as a time base signal.

Time Base Operation

The Time Base operation is a very simple function for

the generation of a regular time signal. This is imple-

mented by generating a regular interrupt signal whose

enable/disabled and request flags are in the INTC regis-

ter. The clock source for the time base is the internal

SYS/4 clock source, which is then divided internally by a

value of 1024. It is this divided signal that generates the

internal interrupt. The Time Base Interrupt is enabled by

the ETBI bit in the INTC register and interrupt request

flag is the TBF flag in the same register. A time base of

1ms will therefor be generated from a system clock of

4MHz and a time base of 0.5ms will be generated from a

system clock source of 8MHz.

Time base Example

The following example program section is based on the

device. The program shows how the Time Base regis-

ters are setup along with how the interrupts are enabled

and managed. The points to note in the example are

how the Time Base is turned on by setting bit 4 of the

INTC register. The Time Base can be turned off in a sim-

ilar way by clearing the same bit. This example program

sets the Time Base which uses the internal system clock

as their clock source, and produces a time base inter-

rupt every 0.5ms from a system source clock of 8MHz.

#include HT83F02.inc

jmp

begin

org 04h

; time base vector

jmp

time_base_int

; jump here when time base overflows per 0.5ms

org 08h

reti

org 0Ch

reti

org 10h

reti

org 14h

reti

; time base interrupt routine

time_base_int:

; time base main program placed here

reti

begin:

; setup interrupt register

mov

a,03h

; enable global and time base interrupt

mov

intc,a

; enable time base

¸ 1 0 2 4

S y s t e m C l o c k / 4

O v e r f l o w

t o I n t e r r u p t

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