HT49CV5 Holtek Semiconductor, HT49CV5 Datasheet - Page 13

• Manufacturer Part Number: HT49CV5
• Description: A/D
• Manufacturer: Holtek Semiconductor

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 (TRF), Timer/Event Coun-
ter 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 register 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.
E M I , EE I0 , EE I1 , E T0I, ET1 I, SB EN , ERT I,
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, TRF, T0F, T1F, EIF1, EIF0) are
all set, they remain in the INTC0~INTC1 respectively
until the interrupts are serviced or cleared by a software
instruction.
It is recommended that a program should not use the
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 CALL in the interrupt subroutine may dam-
age the original control sequence.
Oscillator Configuration
The HT49RV5/HT49CV5 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
Note:
Rev. 1.20
CALL subroutine within the interrupt subroutine. This
32768Hz crystal enable condition: For WDT clock source or for system clock source.
The external resistor and capacitor components connected to the 32768Hz crystal are not necessary to pro-
vide oscillation. For applications where precise RTC frequencies are essential, these components may be re-
quired to provide frequency compensation due to different crystal manufacturing tolerances.
System Oscillator
13
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 56k to
1.5M . 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 QOSC bit (bit 4 of RTCC). It is
recommended to turn on the quick start-up function
during 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 s at 5V. The WDT oscillator
can be disabled by options so as to conserve power.
HT49RV5/HT49CV5
April 14, 2006