HT85F2240 datasheet(91/147 Pages) HOLTEK

91 / 147 page

Rev. 1.10

91 of 147

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A/D Flash 8051 Core Low Pin Count MCU

HT85F2230/HT85F2240

Time Base Interrupts

The function of the Time Base Interrupt is to provide a regular time signal in the form of an

internal interrupt. It is basically a simple timer whose interrupt is generated when it overflows.

When this happen its respective interrupt request flag, TBF will be set. To allow the program to

branch to its respective interrupt vector address, the global interrupt enable bit, EAL and Time

Base enable bit, ETB, must first be set. When the interrupt is enabled, the stack is not full and the

Time Base overflows, a subroutine call to its respective vector locations will take place. When the

interrupt is serviced, the respective interrupt request flag, TBF, will be automatically reset but the

EAL bit must be cleared by the application program to disable other interrupts.

The purpose of the Time Base Interrupt is to provide an interrupt signal at fixed time periods. Their

clock sources originate from the internal clock source fTBC. This fTBC input clock passes through a

divider, the division ratio of which is selected by programming the appropriate bits in the TBCR

controls the Time Base interrupt period, can originate from the system clock or the LIRC oscillator.

Time Base Interr�pt

fTBC

÷�8~�1�

fSYS/4

TBCK[1:0]

TBS[�:0]

f��K

fSYS/1�8

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