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MC9S12H256 Device User Guide — V01.18
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2.3 Detailed Signal Descriptions
2.3.1 EXTAL, XTAL — Oscillator Pins
EXTALandXTALarethecrystaldriverandexternalclockpins.Onresetallthedeviceclocksarederived
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 pin is reserved for test.
NOTE:
The TEST pin must be tied to VSS in all applications.
2.3.4 XFC — PLL Loop Filter Pin
Dedicated pin used to create the PLL loop filter.
2.3.5 BKGD / TAGHI / MODC — Background Debug, Tag High, and Mode Pin
The BKGD/TAGHI/MODC pin is used as a pseudo-open-drain pin for the background debug
communication. In MCU expanded modes of operation when instruction tagging is on, an input low on
this pin during the falling edge of E-clock tags the high half of the instruction word being read into the
instruction queue. 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.
2.3.6 PAD[15:8] / AN[15:8] — Port AD Input Pins [15:8]
PAD15-PAD8 are general purpose input pins and analog inputs for the analog to digital converter.
NOTE:
These pins are not available in the 112-pin LQFP version.
2.3.7 PAD[7:0] / AN[7:0] — Port AD Input Pins [7:0]
PAD7-PAD0 are general purpose input pins and analog inputs for the analog to digital converter.
2.3.8 PA[7:0] / FP[15:8] / ADDR[15:8] / DATA[15:8] — Port A I/O Pins
PA7-PA0 are general purpose input or output pins. They can be configured as frontplane segment driver
outputs FP15-FP8 of the LCD. In MCU expanded modes of operation, these pins are used for the
multiplexed external address and data bus.
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