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Chapter 1 Device Overview MC9S12XE-Family
MC9S12XE-Family Reference Manual , Rev. 1.07
52
Freescale Semiconductor
1.2.3
Detailed Signal Descriptions
NOTE
For devices assembled in 80-pin ,112-pin and 144-pin packages all
non-bonded out pins should be configured as outputs after reset in order to
avoid current drawn from floating inputs. Refer to
Table 1-10
for affected
pins.
1.2.3.1
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 oscillator output.
1.2.3.2
RESET — External Reset Pin
The RESET pin is 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. The RESET pin has an
internal pull-up device.
1.2.3.3
TEST — Test Pin
This input only pin is reserved for test. This pin has a pull-down device.
NOTE
The TEST pin must be tied to V
SS
in all applications.
1.2.3.4
BKGD / MODC — Background Debug and Mode Pin
The BKGD/MODC pin is used as a pseudo-open-drain pin for the background debug communication. It
is used as a MCU operating mode select pin during reset. The state of this pin is latched to the MODC bit
at the rising edge of RESET. The BKGD pin has a pull-up device.
1.2.3.5
PAD[15:0] / AN[15:0] — Port AD Input Pins of ATD0
PAD[15:0] are general-purpose input or output pins and analog inputs AN[15:0] of the analog-to-digital
converter ATD0.
1.2.3.6
PAD[31:16] / AN[31:16] — Port AD Input Pins of ATD1
PAD[31:16]aregeneral-purposeinputoroutputpinsandanaloginputsAN[31:16]oftheanalog-to-digital
converter ATD1.
1.2.3.7
PA[7:0] / ADDR[15:8] / IVD[15:8] — Port A I/O Pins
PA[7:0] are general-purpose input or output pins. In MCU expanded modes of operation, these pins are
used for the external address bus. In MCU emulation modes of operation, these pins are used for external
address bus and internal visibility read data.