HT49R50A-1 View Datasheet(PDF) - Holtek Semiconductor
Part Name
Description
MFG CO.
'HT49R50A-1' PDF : 45 Pages View PDF
HT49R50A-1/HT49C50-1/HT49C50L
The Timer/Event Counter 0 interrupt request flag (T0F),
external interrupt 1 request flag (EIF1), external inter-
rupt 0 request flag (EIF0), enable Timer/Event Counter
0 interrupt bit (ET0I), enable external interrupt 1 bit
(EEI1), enable external interrupt 0 bit (EEI0), and en-
able master interrupt bit (EMI) make up of the Interrupt
Control register 0 (INTC0) which is located at 0BH in the
RAM. The real time clock interrupt request flag (RTF),
time base interrupt request flag (TBF), Timer/Event
Counter 1 interrupt request flag (T1F), enable real time
clock interrupt bit (ERTI), and enable time base interrupt
bit (ETBI), enable Timer/Event Counter 1 interrupt bit
(ET1I) on the other hand, constitute the Interrupt Control
register 1 (INTC1) which is located at 1EH in the RAM.
EMI, EEI0, EEI1, ET0I, ET1I, ETBI, and ERTI are all
used to control the enable/disable status of interrupts.
These bits prevent the requested interrupt from being
serviced. Once the interrupt request flags (RTF, TBF, T0F,
T1F, EIF1, EIF0) are all set, they remain in the INTC1 or
INTC0 respectively until the interrupts are serviced or
cleared by a software instruction.
It is recommended that a program not use the ²CALL
subroutine² within the interrupt subroutine. It¢s because
interrupts often occur in an unpredictable manner or re-
quire to be serviced immediately in some applications. At
this time, if only one stack is left, and enabling the inter-
rupt is not well controlled, operation of the ²call² in the in-
terrupt subroutine may damage the original control
sequence.
Oscillator Configuration
These devices provide three oscillator circuits for sys-
tem clocks, i.e., RC oscillator and crystal oscillator, de-
termined by option. No matter what type of oscillator is
selected, the signal is used for the system clock. The
HALT mode stops the system oscillator and ignores ex-
ternal signal to conserve power.
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 24kW to
1MW for HT49R50A-1/HT49C50-1 and from 560kW to
1MW for HT49C50L. The system clock, divided by 4, is
available on OSC2 with pull-high resistor, which can be
used to synchronize external logic. The RC oscillator
provides the most cost effective solution. However, the
frequency of the oscillation may vary with VDD, temper-
Symbol
Parameter
Min.
fO
Nominal Frequency
¾
ESR
Series Resistance
¾
CL
Load Capacitance
¾
O SC1
V DD
O SC1
V DD
O SC2
fS Y S /4
C r y s ta l O s c illa to r
System Oscillator
O SC2
R C O s c illa to r
O SC3
O SC4
32768Hz Crystal/RTC Oscillator
ature, 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 required 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 ex-
ternal capacitors in OSC1 and OSC2 are required.
There is another oscillator circuit designed for the real
time clock. In this case, only the 32.768kHz crystal oscil-
lator can be applied. The crystal should be connected
between OSC3 and OSC4, and two external capacitors
along with one external resistor are required for the os-
cillator circuit in order to get a stable frequency.
The RTC oscillator circuit can be controlled to oscillate
quickly by setting the ²QOSC² bit (bit 4 of RTCC). It is
recommended to turn on the quick oscillating function
upon power on, and 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 65ms at 5V. The WDT oscillator
can be disabled by option to conserve power.
Typ.
Max.
Unit
32.768
¾
kHz
50
65
kW
9
¾
pF
Note:
1. It is strongly recommended to use a crystal with load capacitance 9pF.
2. The oscillator selection can be optimized using a high quality resonator with small ESR value. Refer to
crystal manufacturer for more details: www.microcrystal.com
Crystal Specifications
Rev. 2.40
13
July 30, 2012
Share Link: 
