HT56R656 datasheet(74/108 Pages) HOLTEK

74 / 108 page

HT56R62/HT56R65

HT56R642/HT56R644/HT56R654/HT56R656

Rev. 1.00

July 20, 2009

Multi-function Interrupt

An additional interrupt known as the Multi-function inter-

rupt is provided. Unlike the other interrupts, this interrupt

has no independent source, but rather is formed from

four or five other existing interrupt sources, namely the

A/D Converter interrupt, Time Base interrupt, Real Time

Clock interrupt, External Peripheral interrupt and the

Timer 2 overflow interrupt.

For a Multi-function interrupt to occur, the global interrupt

enable bit, EMI, and the Multi-function interrupt enable

bit, EMFI, must first be set. An actual Multi-function inter-

rupt will take place when the Multi-function interrupt re-

quest flag, MFF, is set. This will occur when either a Time

Base overflow, a Real Time Clock overflow, an A/D con-

version completion, an External Peripheral Interrupt or

Timer 2 overflow interrupt is generated. When the inter-

rupt is enabled and the stack is not full, and either one of

the interrupts contained within the Multi-function interrupt

occurs, a subroutine call to the Multi-function interrupt

vector at location 018H will take place. When the interrupt

is serviced, the Multi-Function request flag, MFF, will be

automatically reset and the EMI bit will be automatically

cleared to disable other interrupts. However, it must be

noted that the request flags from the original source of the

Multi-function interrupt, namely the Time-Base interrupt,

Real Time Clock interrupt, A/D Converter interrupt, Exter-

nal Peripheral interrupt or Timer 2 overflow interrupt will

not be automatically reset and must be manually reset by

the application program.

Real Time Clock Interrupt

The Real Time Clock Interrupt is contained within the

Multi-function Interrupt.

For a Real Time Clock interrupt to be generated, the

global interrupt enable bit, EMI , Real Time Clock inter-

rupt enable bit, ERTI, and Multi-function interrupt enable

bit, EMFI, must first be set. An actual Real Time Clock

interrupt will take place when the Real Time Clock re-

quest flag, RTF, is set, a situation that will occur when

the Real Time Clock overflows. When the interrupt is en-

abled, the stack is not full and the Real Time Clock over-

flows, a subroutine call to the Multi-function interrupt

vector at location18H, will take place. When the Real

Time Clock interrupt is serviced, the EMI bit will be

cleared to disable other interrupts, however only the

MFF interrupt request flag will be reset. As the RTF flag

will not be automatically reset, it has to be cleared by the

application program.

Similar in operation to the Time Base interrupt, the pur-

pose of the RTC interrupt is also to provide an interrupt

signal at fixed time periods. The RTC interrupt clock

source originates from the internal clock source fS. This

fS input clock first passes through a divider, the division

ratio of which is selected by programming the appropri-

ate bits in the RTCC register to obtain longer RTC inter-

rupt periods whose value ranges from 2

8/f

S~2

15/f

S. The

clock source that generates fS, which in turn controls the

RTC interrupt period, can originate from three different

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

D i v i d e b y 2 8 ~ 2 1 5

S e t b y R T C C

R e g i s t e r

f S

R T C I n t e r r u p t

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

R T 2

R T 1

R T 0

RTC Interrupt

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

HT56R656 Datasheet(PDF) 74 Page - Holtek Semiconductor Inc

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