MC9S12Q128_10 Datasheet, PDF (51/644 Pages) Freescale Semiconductor, Inc – HCS12 Microcontrollers

Chapter 1 MC9S12Q Device Overview (MC9S12Q128-Family)
1.3.4.6 PA[7:0] / ADDR[15:8] / DATA[15:8] — Port A I/O Pins
PA7–PA0 are general purpose input or output pins,. In MCU expanded modes of operation, these pins are
used for the multiplexed external address and data bus. PA[7:1] pins are not available in the 48-pin package
version. PA[7:3] are not available in the 52-pin package version.
1.3.4.7 PB[7:0] / ADDR[7:0] / DATA[7:0] — Port B I/O Pins
PB7–PB0 are general purpose input or output pins. In MCU expanded modes of operation, these pins are
used for the multiplexed external address and data bus. PB[7:5] and PB[3:0] pins are not available in the
48-pin nor 52-pin package version.
1.3.4.8 PE7 / NOACC / XCLKS — Port E I/O Pin 7
PE7 is a general purpose input or output pin. During MCU expanded modes of operation, the NOACC
signal, when enabled, is used to indicate that the current bus cycle is an unused or “free” cycle. This signal
will assert when the CPU is not using the bus.The XCLKS is an input signal which controls whether a
crystal in combination with the internal Colpitts (low power) oscillator is used or whether Pierce
oscillator/external clock circuitry is used. The state of this pin is latched at the rising edge of RESET. If
the input is a logic low the EXTAL pin is configured for an external clock drive or a Pierce oscillator. If
input is a logic high a Colpitts oscillator circuit is configured on EXTAL and XTAL. Since this pin is an
input with a pull-up device during reset, if the pin is left floating, the default configuration is a Colpitts
oscillator circuit on EXTAL and XTAL.
EXTAL
MCU
XTAL
CDC¹
C₁
C₂
Crystal or
Ceramic Resonator
V_SSPLL
1. Due to the nature of a translated ground Colpitts oscillator a DC voltage
bias is applied to the crystal. Please contact the crystal manufacturer for
crystal DC.
Figure 1-10. Colpitts Oscillator Connections (PE7 = 1)
EXTAL
MCU
XTAL
R_B
R_S1
C₁
Crystal or
Ceramic Resonator
C₂
V_SSPLL
1. RS can be zero (shorted) when used with higher frequency crystals,
refer to manufacturer’s data.
Figure 1-11. Pierce Oscillator Connections (PE7 = 0)
Freescale Semiconductor
MC9S12Q128
51
Rev 1.10