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Chapter 1 MC9S12XF-Family Reference Manual
MC9S12XF - Family Reference Manual, Rev.1.19
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Freescale Semiconductor
1.2.8.3
PB[7:1] / ADDR[7:1] / IVD[7:1] — Port B I/O Pins
PB7-PB1 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.
1.2.8.4
PB0 / ADDR0 / UDS / IVD[0] — Port B I/O Pin
PB0 is a general purpose input or output pin. In MCU expanded modes of operation, this pin is used for
the external address bus ADDR0 or as upper data strobe signal. In MCU emulation modes of operation,
this pin is used for external address bus ADDR0 and internal visibility read data IVD0.
1.2.8.5
PC[7:0] / DATA [15:8] — Port C I/O Pins
PC7-PC0 are general purpose input or output pins. In MCU expanded modes of operation, these pins are
used for the external data bus.
The input voltage thresholds for PC[7:0] can be congured to reduced levels, to allow data from an external
3.3V peripheral to be read by the MCU operating at 5.0V. The input voltage thresholds for PC[7:0] are
congured to reduced levels out of reset in expanded and emulation modes. The input voltage thresholds
for PC[7:0] are congured to 5V levels out of reset in normal modes.
1.2.8.6
PD[7:0] / DATA [7:0] — Port D I/O Pins
PD7-PD0 are general purpose input or output pins. In MCU expanded modes of operation, these pins are
used for the external data bus.
The input voltage thresholds for PD[7:0] can be congured to reduced levels, to allow data from an
external 3.3V peripheral to be read by the MCU operating at 5.0V. The input voltage thresholds for
PD[7:0] are congured to reduced levels out of reset in expanded and emulation modes. The input voltage
thresholds for PC[7:0] are congured to 5V levels out of reset in normal modes.
1.2.8.7
PE7 / ECLKX2 / XCLKS — Port E I/O
PE7 is a general-purpose input or output pin. ECLKX2 is a free running clock of twice the internal bus
frequency, available by default in emulation modes and when enabled in other modes. 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
Oscillator1.2.8.8
PE6 / MODB / TAGHI — Port E I/O
PE6 is a general purpose input or output pin. It is used as a MCU operating mode select pin during reset.
The state of this pin is latched to the MODB bit at the rising edge of RESET. This pin is an input with a
pull-down device which is only active when RESET is low. TAGHI is used to tag the high half of the
instruction word being read into the instruction queue.