mc9s08sh8mwjr Freescale Semiconductor, Inc, mc9s08sh8mwjr Datasheet - Page 26

• Manufacturer Part Number: mc9s08sh8mwjr
• Description: S08sh 5-volt 8-bit Microcontrollers With Sci, Spi, I2c, Adc And Analog Comparators
• Manufacturer: Freescale Semiconductor, Inc

Chapter 2 Pins and Connections
2.2.1
V
I/O buffer circuitry and to an internal voltage regulator. The internal voltage regulator provides regulated
lower-voltage source to the CPU and other internal circuitry of the MCU.
Typically, application systems have two separate capacitors across the power pins. In this case, there
should be a bulk electrolytic capacitor, such as a 10-μF tantalum capacitor, to provide bulk charge storage
for the overall system and a 0.1-μF ceramic bypass capacitor located as near to the MCU power pins as
practical to suppress high-frequency noise. Each pin must have a bypass capacitor for best noise
suppression.
V
ADC module. A 0.1uF ceramic bypass capacitor should be located as near to the MCU power pins as
practical to suppress high-frequency noise. The V
voltage reference low inputs, respectively for the ADC module. For this MCU, V
pin and these pins are available only in the 28-pin packages. In the 16-pin and 20-pin packages they are
double bonded to the V
in the 28-pin packages. In the 16-pin and 20-pin packages they are double bonded to the V
2.2.2
Immediately after reset, the MCU uses an internally generated clock provided by the clock source
generator (ICS) module. For more information on the ICS, see
(S08ICSV2).”
The oscillator (XOSC) in this MCU is a Pierce oscillator that can accommodate a crystal or ceramic
resonator. Rather than a crystal or ceramic resonator, an external oscillator can be connected to the EXTAL
input pin.
Refer to
resistors such as carbon composition resistors. Wire-wound resistors, and some metal film resistors, have
too much inductance. C1 and C2 normally should be high-quality ceramic capacitors that are specifically
designed for high-frequency applications.
R
is not generally critical. Typical systems use 1 MΩ to 10 MΩ. Higher values are sensitive to humidity and
lower values reduce gain and (in extreme cases) could prevent startup.
C1 and C2 are typically in the 5-pF to 25-pF range and are chosen to match the requirements of a specific
crystal or resonator. Be sure to take into account printed circuit board (PCB) capacitance and MCU pin
capacitance when selecting C1 and C2. The crystal manufacturer typically specifies a load capacitance
which is the series combination of C1 and C2 (which are usually the same size). As a first-order
approximation, use 10 pF as an estimate of combined pin and PCB capacitance for each oscillator pin
(EXTAL and XTAL).
26
F
DD
DDA
is used to provide a bias path to keep the EXTAL input in its linear range during crystal startup; its value
and V
and V
Figure 2-4
Power
Oscillator (XOSC)
SS
SSA
are the primary power supply pins for the MCU. This voltage source supplies power to all
are the analog power supply pins for MCU. This voltage source supplies power to the
for the following discussion. R
DD
pin. For this MCU, V
MC9S08SH32 Series Data Sheet, Rev. 2
PRELIMINARY
SSA
REFH
S
shares the V
(when used) and R
and V
REFL
Chapter 11, “Internal Clock Source
REFL
pins are the voltage reference high and
pin and these pins are available only
F
should be low-inductance
DDA
Freescale Semiconductor
shares the V
SS
pin.
REFH