Техническая Спецификация для Freescale Semiconductor DEMO9S08DZ60 Demo Board DEMO9S08DZ60 DEMO9S08DZ60
Модели
DEMO9S08DZ60
Chapter 2 Pins and Connections
MC9S08DZ60 Series Data Sheet, Rev. 4
Freescale Semiconductor
31
2.2.1
Power
V
DD
and V
SS
are the primary power supply pins for the MCU. This voltage source supplies power to all
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.
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-
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. The MC9S08DZ60 Series has two V
DD
pins except on the
32-pin package. Each pin must have a bypass capacitor for best noise suppression.
V
DDA
and V
SSA
are the analog power supply pins for the MCU. This voltage source supplies power to the
ADC module. A 0.1-
μF ceramic bypass capacitor should be located as near to the MCU power pins as
practical to suppress high-frequency noise.
2.2.2
Oscillator
Immediately after reset, the MCU uses an internally generated clock provided by the multi-purpose clock
generator (MCG) module. For more information on the MCG, see
generator (MCG) module. For more information on the MCG, see
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.
resonator. Rather than a crystal or ceramic resonator, an external oscillator can be connected to the EXTAL
input pin.
Refer to
for the following discussion. R
S
(when used) and R
F
should be low-inductance
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.
too much inductance. C1 and C2 normally should be high-quality ceramic capacitors that are specifically
designed for high-frequency applications.
R
F
is used to provide a bias path to keep the EXTAL input in its linear range during crystal startup; its value
is not generally critical. Typical systems use 1 M
Ω 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).
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).
2.2.3
RESET
RESET is a dedicated pin with a pull-up device built in. It has input hysteresis, a high current output driver,
and no output slew rate control. Internal power-on reset and low-voltage reset circuitry typically make
external reset circuitry unnecessary. This pin is normally connected to the standard 6-pin background
debug connector so a development system can directly reset the MCU system. If desired, a manual external
reset can be added by supplying a simple switch to ground (pull reset pin low to force a reset).
and no output slew rate control. Internal power-on reset and low-voltage reset circuitry typically make
external reset circuitry unnecessary. This pin is normally connected to the standard 6-pin background
debug connector so a development system can directly reset the MCU system. If desired, a manual external
reset can be added by supplying a simple switch to ground (pull reset pin low to force a reset).