MC9S12A128 Datasheet, PDF (28/92 Pages) Motorola, Inc – Microcontroller unit (MCU)

MC9S12A128 Device Guide — V01.01
2.3 Detailed Signal Descriptions
2.3.1 EXTAL, XTAL — Oscillator Pins
EXTAL and XTAL are the crystal driver and external clock pins. On reset all the device clocks are derived
from the EXTAL input frequency. XTAL is the crystal output.
2.3.2 RESET — External Reset Pin
An active low bidirectional control signal, it acts as an input to initialize the MCU to a known start-up state,
and an output when an internal MCU function causes a reset.
2.3.3 TEST — Test Pin
This input only pin is reserved for test.
NOTE: The TEST pin must be tied to V_SS in all applications.
2.3.4 V_REGEN — Voltage Regulator Enable Pin
This input only pin enables or disables the on-chip voltage regulator.
2.3.5 XFC — PLL Loop Filter Pin
PLL loop filter, see A.5.3 Phase Locked Loop. If needed, contact your Motorola representative for the
interactive application note to compute PLL loop filter elements. Any current leakage on this pin must be
avoided.
XFC
MCU
R₀
C_S
V_DDPLL
C_P
V_DDPLL
Figure 2-3 PLL Loop Filter Connections
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