HT48CA0-1 Holtek Semiconductor, HT48CA0-1 Datasheet - Page 7

• Manufacturer Part Number: HT48CA0-1
• Description: (HT48RA0-1 / HT48CA0-1) Remote Type 8-Bit MCU
• Manufacturer: Holtek Semiconductor

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Oscillator Configuration
There are two oscillator circuits implemented in the
microcontroller.
Both are designed for system clocks; the RC oscillator
and the Crystal oscillator, which are determined by code
options. No matter what oscillator type is selected, the
signal provides the system clock. The HALT mode stops
the system oscillator and ignores the external signal to
conserve power.
If an RC oscillator is used, an external resistor between
OSC1 and VSS in needed and the resistance must
range from 51k to 1M . The system clock, divided by
4, is available on OSC2, which can be used to synchro-
nize external logic. The RC oscillator provides the most
Rev. 1.40
Bit No.
6~7
0
1
2
3
4
5
Label
PDF
AC
OV
TO
C
Z
System Oscillator
C is set if the operation results in a carry during an addition operation or if a borrow does not
take place during a subtraction operation; otherwise C is cleared. C is also affected by a ro-
tate through carry instruction.
AC is set if the operation results in a carry out of the low nibbles in addition or no borrow from
the high nibble into the low nibble in subtraction; otherwise AC is cleared.
Z is set if the result of an arithmetic or logic operation is zero; otherwise Z is cleared.
OV is set if the operation results in a carry into the highest-order bit but not a carry out of the
highest-order bit, or vice versa; otherwise OV is cleared.
PDF is cleared when either a system power-up or executing the CLR WDT instruction. PDF
is set by executing the HALT instruction.
TO is cleared by a system power-up or executing the CLR WDT or HALT instruction. TO is
set by a WDT time-out.
Unused bit, read as 0
Status (0AH) Register
Watchdog Timer
7
cost effective solution. However, the frequency of the
oscillation may vary with V
itself due to process variations. It is, therefore, not suit-
able for timing sensitive operations where accurate os-
cillator frequency is desired.
If the Crystal oscillator is used, a crystal across OSC1
and OSC2 is needed to provide the feedback and phase
shift for the oscillator. No other external components are
needed. Instead of a crystal, the resonator can also be
connected between OSC1 and OSC2 to get a frequency
reference, but two external capacitors in OSC1 and
OSC2 are required.
Watchdog Timer - WDT
The clock source of the WDT is implemented by instruc-
tion clock (system clock divided by 4). The clock source
is processed by a frequency divider and a prescaller to
yield various time out periods.
WDT time out period =
Where n= 8~11 selected by code option.
Function
HT48RA0-1/HT48CA0-1
Clock Source
DD
, temperature and the chip
2
n
December 21, 2005