
MC68HC908EY16A MC68HC908EY8A Data Sheet, Rev. 2
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Freescale Semiconductor
1.5.6 Port A I/O Pins (PTA6/SS, PTA5/SPSCK, PTA4/KBD4, PTA3/KBD3/RxD,
PTA2/KBD2/TxD, PTA1/KBD1, and PTA0/KBD0)
Port A input/output (I/O) pins (PTA6/SS, PTA5/SPSCK, PTA4/KBD4, PTA3/KBD3/RxD,
PTA2/KBD2/TxD, PTA1/KBD1, and PTA0/KBD0) are special-function, bidirectional I/O port pins. PTA5
and PTA6 are shared with the serial peripheral interface (SPI). PTA4-PTA0 can be programmed to serve
as keyboard interrupt pins. PTA2 and PTA3 can be programmed to serve as the ESCI transmit and
receive data pins.
1.5.7 Port B I/O Pins (PTB7/AD7/TBCH1, PTB6/AD6/TBCH0, PTB5/AD5/SPSCK,
PTB4/AD4/MOSI, PTB3/AD3/MISO, PTB2/AD2–PTB0/AD0)
PTB7/AD7/TBCH1, PTB6/AD6/TBCH0, PTB5/AD5/SPSCK, PTB4/AD4/MOSI, PTB3/AD3/MISO,
PTB2/AD2–PTB0/AD0 are special-function, bidirectional I/O port pins that can also be used for ADC
inputs. PTB7/AD7/TBCH1 and PTB6/AD6/TBCH0 are special function bidirectional I/O port pins that can
also be used for timer interface pins. PTB5/AD5/SPSCK, PTB4/AD4/MOSI, and PTB3/AD3/MISO can be
programmed to serve as SPI clock and data pins.
1.5.8 Port C I/O Pins (PTC4/OSC1, PTC3/OSC2, PTC2/MCLK/SS, PTC1/MOSI, PTC0/MISO)
PTC4/OSC1, PTC3/OSC2, PTC2/MCLK/SS, PTC1/MOSI, PTC0/MISO are special-function, bidirectional
When applications require:
PTC3/OSC2 can be programmed to be OSC2
PTC4/OSC1 can be programmed to be OSC1
PTC2/MCLK/SS is software selectable to be MCLK, or bus clock out. PTC1/MOSI can be programmed
to be the MOSI signal for the SPI. PTC0/MISO can be programmed to be the MISO signal for the SPI.
1.5.9 Port D I/O Pins (PTD1/TACH1–PTD0/TACH0)
PTD1/TACH1–PTD0/TACH0 are special-function, bidirectional I/O port pins that can also be programmed
to be timer pins.
1.5.10 Port E I/O Pins (PTE1/RxD–PTE0/TxD)
PTE1/RxD–PTE0/TxD are special-function, bidirectional I/O port pins that can also be programmed to be
enhanced serial communication interface (ESCI) pins.