General Description
MC68HC908GT16 MC68HC908GT8 Data Sheet, Rev. 3
24
Freescale Semiconductor
Figure 1-4. Power Supply Bypassing
1.5.2 Oscillator Pins (PTE4/OSC1 and PTE3/OSC2)
PTE4/OSC1 and PTE3/OSC2 are general-purpose, bidirectional I/O port pins. These pins can also be
programmed to be the connections for an external crystal, resonator or clock circuit. See
Chapter 7
Internal Clock Generator (ICG) Module)
.
1.5.3 External Reset Pin (RST)
A logic 0 on the RST pin forces the MCU to a known startup state. RST is bidirectional, allowing a reset
of the entire system. It is driven low when any internal reset source is asserted. This pin contains an
internal pullup resistor. See
Chapter 15 System Integration Module (SIM).
1.5.4 External Interrupt Pin (IRQ)
IRQ is an asynchronous external interrupt pin. This pin contains an internal pullup resistor. See
Chapter 8 External Interrupt (IRQ).
1.5.5 ADC and ICG Power Supply Pins (V
DDA
and V
SSA
)
V
DDA
and V
SSA
are the power supply pins for the analog-to-digital converter (ADC) and the internal clock
generator (ICG). Connect the V
DDA
pin to the same voltage potential as V
DD
, and the
V
SSA
pin to the
same voltage potential as V
SS
. Decoupling of these pins should be as per the digital supply. See
Chapter 3 Analog-to-Digital Converter (ADC)
and
Chapter 7 Internal Clock Generator (ICG) Module)
.
1.5.6 ADC Reference Pins (V
REFH
and V
REFL
)
V
REFH
and V
REFL
are the reference voltage pins for the analog-to-digital converter (ADC). V
REFH
is the
high reference supply for the ADC and should be filtered. V
REFH
must be connected to the same voltage
potential as the analog supply pin, V
DDA
. V
REFL
is the low reference supply for the ADC and should be
externally filtered. V
REFL
must be connected to the same voltage potential as the analog supply pin V
SSA
.
See
Chapter 3 Analog-to-Digital Converter (ADC)
.
MCU
V
DD
C2
C1
0.1
μ
F
V
SS
V
DD
+
Note: Component values shown represent typical applications.