Pinout and Signal Descriptions
68HC(9)12DG128 Rev 1.0
28
Pinout and Signal Descriptions
MOTOROLA
Power Supply Pins
68HC(9)12DG128 power and ground pins are described below and
summarized in
Table 6
.
Internal Power
(V
DD
) and Ground
(V
SS
)
Power is supplied to the MCU through V
DD
and V
SS
. Because fast signal
transitions place high, short-duration current demands on the power
supply, use bypass capacitors with high-frequency characteristics and
place them as close to the MCU as possible. Bypass requirements
depend on how heavily the MCU pins are loaded.
External Power
(V
DDX
)
and
Ground (V
SSX
)
External power and ground for I/O drivers. Because fast signal
transitions place high, short-duration current demands on the power
supply, use bypass capacitors with high-frequency characteristics and
place them as close to the MCU as possible. Bypass requirements
depend on how heavily the MCU pins are loaded.
V
DDA
, V
SSA
Provides operating voltage and ground for the analog-to-digital
converter. This allows the supply voltage to the ATD to be bypassed
independently. Connecting V
DDA
to V
DD
if the ATD modules are not
used will not result in an increase of power consumption.
Analog to Digital
Reference
Voltages (V
RH
, V
RL
)
V
RH0
, V
RL0
: reference voltage high and low for ATD converter 0.
V
RH1
, V
RL1
: reference voltage high and low for ATD converter 1.
If the ATD modules are not used, leaving V
RH
connected to V
DD
will not
result in an increase of power consumption.
V
DDPLL
, V
SSPLL
Provides operating voltage and ground for the Phased-Locked Loop.
This allows the supply voltage to the PLL to be bypassed independently.
NOTE:
The VSSPLL pin should always be grounded even if the PLL is not used.
The VDDPLL pin should not be left floating. It is recommended to
connect the VDDPLL pin to ground if the PLL is not used.
4-pins