HT48RA0-5 Holtek Semiconductor, HT48RA0-5 Datasheet - Page 8

• Manufacturer Part Number: HT48RA0-5
• Description: Remote Type 8-Bit OTP MCU
• Manufacturer: Holtek Semiconductor

In addition, on executing a subroutine call, the status
register will not be automatically pushed onto the stack.
If the contents of the status are important and if the sub-
routine can corrupt the status register, precautions must
be taken to save it properly.
Oscillator Configuration
In this device there are two methods of generating the
system clock, one external crystal oscillator and one in-
ternal RC oscillator.
Rev.1.00
External Crystal/Resonator Oscillator
The External Crystal/Ceramic System Oscillator is
one of the system oscillator choices, which is selected
via a configuration option. For the crystal oscillator
configuration, the connection of a crystal across
OSC1 and OSC2 will create the necessary phase shift
and feedback for oscillation. Two external capacitors
may be required to be connected as shown. However,
the feedback resistor named Rf shown in the following
diagram for the crystal oscillator to oscillate properly
can be selected as either an internally or externally
connected type via a configuration option. When the
external connection type of the feedback resistor is
selected, the recommended value of the external con-
nected feedback resistor ranges from 300k
500k [. Using a ceramic resonator will usually require
two small value capacitors, C1 and C2, to be con-
nected as shown for oscillation to occur. The values of
C1 and C2 should be selected in consultation with the
crystal or resonator manufacturer s specification.
Crystal/Resonator Oscillator - HXT
HXT
to
8
Crystal Frequency
4MHz
Note: C1 and C2 values are for guidance only.
Internal RC Oscillator
The internal RC oscillator is a fully integrated system
oscillator requiring no external components. The inter-
nal RC oscillator has a fixed frequency of 4095kHz.
Device trimming during the manufacturing process
and the inclusion of internal frequency compensation
circuits are used to ensure that the influence of the
power supply voltage, temperature and process varia-
tions on the oscillation frequency are minimised. As a
result, at a power supply ranging from 1.8V to 3.6V
and in a temperature range from -10 C to 50 C de-
grees, the fixed oscillation frequency of 4095kHz will
have a tolerance within 2%. Note that if this internal
system clock option is selected, as it requires no ex-
ternal pins for its operation, I/O pins PB5 and PB6 are
free for use as normal I/O pins.
Crystal Recommended Capacitor Values
Crystal Oscillator C1 and C2 Values
HIRC
8pF
C1
HT48RA0-5
March 23, 2010
www.DataSheet4U.com
10pF
C2