HT45R37 datasheet(57/100 Pages) HOLTEK

57 / 100 page

HT45R37

Rev. 1.10

January 29, 2010

flows. When the interrupt is enabled, the stack is not full

and the Time Base overflows, a subroutine call to the

Multi-function Interrupt 1 vector at location18H, will take

place. When the Time Base Interrupt is serviced, the

EMI bit will be cleared to disable other interrupts, how-

ever only the MF1F interrupt request flag will be reset.

As the TBF flag will not be automatically reset, it has to

be cleared by the application program.

The purpose of the Time Base function is to provide an

interrupt signal at fixed time periods. The Time Base in-

terrupt clock source originates from the Time Base inter-

rupt clock source originates from the internal clock

source fS. This fS input clock first passes through a di-

vider, the division ratio of which is selected by configura-

tion options to provide longer Time Base interrupt

periods. The Time Base interrupt time-out period ranges

from 2

12/f

S~2

15/f

S. The clock source that generates fS,

which in turn controls the Time Base interrupt period,

can originate from three different sources, the 32768Hz

oscillator, the 32K_INT internal oscillator or the System

oscillator/4, the choice of which is determine by the fS

clock source configuration option.

Essentially operating as a programmable timer, when

the Time Base overflows it will set a Time Base interrupt

flag which will in turn generate an Interrupt request via

the Multi-function Interrupt 1 vector.

Programming Considerations

By disabling the interrupt enable bits, a requested inter-

rupt can be prevented from being serviced, however,

once an interrupt request flag is set, it will remain in this

condition in the INTC0, INTC1, MFIC0 and MFIC1 reg-

isters until the corresponding interrupt is serviced or un-

til the request flag is cleared by the application program.

Note that if a specific interrupt uses a Multi-function In-

terrupt vector then its interrupt request flag will not be

automatically reset when the program enters the inter-

rupt service routine. Only the Multi-function interrupt re-

quest flag will be automatically reset.

It is recommended that programs do not use the

²CALL

subroutine

² instruction within the interrupt subroutine.

Interrupts often occur in an unpredictable manner or

need to be serviced immediately in some applications. If

only one stack is left and the interrupt is not well con-

trolled, the original control sequence will be damaged

once a

²CALL subroutine² is executed in the interrupt

subroutine.

All of these interrupts have the capability of waking up

the processor when in the Power Down Mode.

Only the Program Counter is pushed onto the stack. If

the contents of the status or other registers are altered

by the interrupt service program, which may corrupt the

desired control sequence, then the contents should be

saved in advance.

R T C C R e g i s t e r

b 7

b 0

L V D O Q O S C L V D C

R T 2

R T 1

R T 0

R T 2

R T 1

R T 0

P e r i o d

2 8 / f S

2 9 / f S

2 1 0 / f S

2 1 1 / f S

2 1 2 / f S

2 1 3 / f S

2 1 4 / f S

2 1 5 / f S

R T C I n t e r r u p t P e r i o d

L o w V o l t a g e D e t e c t o r C o n t r o l

1 : e n a b l e

0 : d i s a b l e

R T C O s c i l l a t o r Q u i c k - s t a r t

1 : d i s a b l e

0 : e n a b l e

L o w V o l t a g e D e t e c t o r O u t p u t

1 : l o w v o l t a g e d e t e c t e d

0 : n o r m a l v o l t a g e

N o t i m p l e m e n t e d , r e a d a s " 0 "

Real Time Clock Control Register

- RTCC

f S S o u r c e

C o n f i g u r a t i o n

O p t i o n

f S Y S / 4

3 2 7 6 8 H z

3 2 K _ I N T

C o n f i g u r a t i o n O p t i o n

D i v i d e b y 2 1 2 ~ 2 1 5

f S

T i m e B a s e I n t e r r u p t

2 1 2 / f S ~ 2 1 5 / f S

Time Base Interrupt

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