S912XHY128F0VLM Datasheet, PDF (42/802 Pages) Freescale Semiconductor, Inc – S12 Microcontrollers

Device Overview MC9S12XHY-Family
1.7.3 Detailed Signal Descriptions
1.7.3.1 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 internal reference clock. XTAL is the oscillator output.
1.7.3.2 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.
1.7.3.3 TEST — Test Pin
This input only pin is reserved for factory test. This pin has an internal pull-down device.
NOTE
The TEST pin must be tied to V_SSA in all applications.
1.7.3.4 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 an internal pull-up device.
1.7.3.5 PAD[7:0] / AN[7:0] / KWAD[7:0]— Port AD Input Pins of ATD [7:0]
PAD[7:0] are a general-purpose input or output pins and analog inputs AN[7:0] of the analog-to-digital
converter ATD. They can be configured as keypad wakeup inputs.
1.7.3.6 PA[7:4] / FP[36:33]— Port A I/O Pins [7:4]
PA[7:4] are a general-purpose input or output pins. They can be configured as frontplane segment driver
outputs FP[36:33].
1.7.3.7 PA[3:2] / API_EXTCLK / XCLKS / FP[32:31]— Port A I/O Pins [3:2]
PA[3:2] are a general-purpose input or output pins. They can be configured as frontplane segment driver
outputs FP[32:31]. PA3 can also be configure as API_EXTCLK.The XCLKS is an input signal which
controls whether a crystal in combination with the internal loop controlled Pierce oscillator is used or
whether full swing Pierce oscillator/external clock circuitry is used (refer to Section 1.16, “Oscillator
Configuration ). An internal pull-down is enabled during reset.
MC9S12XHY-Family Reference Manual, Rev. 1.01
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Freescale Semiconductor