HT49CV7 datasheet(13/48 Pages) HOLTEK

13 / 48 page

HT49RV7/HT49CV7

Rev. 1.00

April 20, 2006

interrupt bit (ET0I), enable external interrupt 1 bit (EEI1),

enable external interrupt 0 bit (EEI0), and enable master

interrupt bit (EMI) constitute the Interrupt Control regis-

ter 0 (INTC0) which is located at 0BH in the RAM.

The multi-function interrupt request flag (MFF), serial in-

terface interrupt request flag (TDRF), Timer/Event

Counter 1 interrupt request flag (T1F), enable

multi-function interrupt (EMFI), enable serial interface

interrupt bit (ESBI), and enable Timer/Event Counter 1

interrupt bit (ET1I), constitute the Interrupt Control regis-

ter 1 (INTC1) which is located at 1EH in the RAM.

The enable Remote control timer rising edge interrupt

(ERMT0), enable Remote control timer falling edge in-

terrupt (ERMT1), enable Remote control timer overflow

interrupt (ERMTV), enable Remote control timer start

counting (RME), select the Remote control timer clock

source (RMCS), and select the Remote control timer

clock (RMS0, RMS1) constitute the Remote Timer con-

trol Register (RMTC) which is located at 21H in the

RAM.

EMI, EEI0, EEI1, ET0I, ET1I, SBEN, ERTI,

EMFI,ERMT0 and ERMT1 are all used to control the en-

able/disable status of interrupts. These bits prevent the

requested interrupt from being serviced. Once the inter-

rupt request flags (MFF, TDRF, T0F, T1F, EIF1, EIF0)

are all set, they remain in the INTC0~INTC1 respec-

tively until the interrupts are serviced or cleared by a

software instruction.

It is recommended that a program should not use the

²CALL subroutine² within the interrupt subroutine. This

is because interrupts often occur in an unpredictable

manner or require to be serviced immediately in some

applications. During that period, if only one stack is left,

and enabling the interrupt is not well controlled, opera-

tion of the

²CALL² in the interrupt subroutine may dam-

age the original control sequence.

Oscillator Configuration

The HT49RV7/HT49CV7 provides three oscillator cir-

cuits for system clocks, i.e., RC oscillator, crystal oscilla-

tor and 32768Hz crystal oscillator, determined by

options. No matter what type of oscillator is selected, the

signal is used for the system clock. The HALT mode

stops the system oscillator (RC and crystal oscillator

only) and ignores external signals so as to conserve

power. The 32768Hz crystal oscillator still runs in the

HALT mode. If the 32768Hz crystal oscillator is selected

as the system oscillator, the system oscillator is not

stopped but the instruction execution is stopped. Since

the 32768Hz oscillator is also designed for timing pur-

poses, the internal timing (RTC, WDT) operation still

runs even if the system enters the HALT mode.

Of the three oscillators, if the RC oscillator is used, an

external resistor between OSC1 and VSS is required,

and the range of the resistance should be from 24k

W to

W. The system clock, divided by 4, is available on

OSC2 with pull-high resistor, which can be used to syn-

chronize external logic. The RC oscillator provides the

most cost effective solution. However, the frequency of

the oscillation may vary with VDD, temperature, and the

chip itself due to process variations. It is therefore not

suitable for timing sensitive operations where accurate

oscillator frequency is desired.

On the other hand, if the crystal oscillator is selected, a

crystal across OSC1 and OSC2 is needed to provide the

feedback and phase shift for the oscillator, and no other

external components are required. A resonator may be

connected between OSC1 and OSC2 to replace the

crystal and to get a frequency reference, but two exter-

nal capacitors on OSC1 and OSC2 are required.

There is another oscillator circuit designed for the real

time clock. In this case, only a 32768Hz crystal oscillator

can be applied. The crystal should be connected be-

tween OSC3 and OSC4.

The RTC oscillator circuit can be controlled to start-up

quickly by setting the

²QOSC² bit (bit 4 of RTCC). It is

recommended to turn on the quick start-up function dur-

ing power-on, and then turn it off after 2 seconds.

The WDT oscillator is a free running on-chip RC oscilla-

tor and no external components are required. Although

the system enters the power down mode, the system

clock stops and the WDT oscillator still works with a pe-

riod of approximately 65

ms at 5V. The WDT oscillator

can be disabled by options so as to conserve power.

C r y s t a l O s c i l l a t o r

R C O s c i l l a t o r

O S C 1

O S C 2

f S Y S / 4

O S C 2

3 2 7 6 8 H z C r y s t a l / R T C O s c i l l a t o r

O S C 3

O S C 4

V D D

4 7 0 p F

V D D

System Oscillator

Note: *32768Hz crystal enable condition: For WDT clock source or for system clock source.

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