S912XEG128J2MAA Datasheet, PDF (62/1324 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 1 Device Overview MC9S12XE-Family
1.2.3
Detailed Signal Descriptions
NOTE
The pin list of the largest package version of each MC9S12XE-Family
derivative gives the complete of interface signals that also exist on smaller
package options, although some of them are not bonded out. For devices
assembled in smaller 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. Particular attention is
drawn to Port R, which does not have enabled pull-up/pull-down devices
coming out of reset.
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. As an output it is driven low to indicate when any internal MCU reset source triggers.
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] are general-purpose input or output pins and analog inputs AN[31:16] of the analog-to-digital
converter ATD1.
MC9S12XE-Family Reference Manual Rev. 1.25
62
Freescale Semiconductor