Pinout and Signal Descriptions
Port Signals
68HC(9)12DG128 Rev 1.0
MOTOROLA
Pinout and Signal Descriptions
43
19-pins
Setting the RDPK bit in register RDRIV causes all port K outputs to have
reduced drive level. RDRIV can be written once after reset. RDRIV is not
in the address map in peripheral mode. Refer to
Bus Control and
Input/Output
.
Port CAN1
The MSCAN1 uses two external pins, one input (RxCAN1) and one
output (TxCAN1). The TxCAN1 output pin represents the logic level on
the CAN: ‘0’ is for a dominant state, and ‘1’ is for a recessive state.
RxCAN1 is on bit 0 of Port CAN1, TxCAN1 is on bit 1.
Port CAN0
The MSCAN0 uses two external pins, one input (RxCAN0) and one
output (TxCAN0). The TxCAN0 output pin represents the logic level on
the CAN: ‘0’ is for a dominant state, and ‘1’ is for a recessive state.
RxCAN0 is on bit 0 of Port CAN0, TxCAN0 is on bit 1.
Port IB
Bidirectional pins to IIC bus interface subsystem. The IIC bus interface
uses a Serial Data line (SDA) and Serial Clock line (SCL) for data
transfer. The pins are connected to a positive voltage supply via a pull
up resistor. The pull ups can be enabled internally or connected
externally. The output stages have open drain outputs in order to
perform the wired-AND function. When the IIC is disabled the pins can
be used as general purpose I/O pins. SCL is on bit 7 of Port IB and SDA
is on bit 6. The remaining two pins of Port IB are controlled by registers
in the IIC address space.
Register DDRIB determines pin direction of port IB when used for
general-purpose I/O. When DDRIB bits are set, the corresponding pin is
configured for output. On reset the DDRIB bits are cleared and the
corresponding pin is configured for input.
When the PUPIB bit in the IBPURD register is set, all input pins are
pulled up internally by an active pull-up device. Pull-ups are disabled
after reset, except for input ports 0 through 3, which are always on
regardless of PUPIB bit.
Setting the RDPIB bit in the IBPURD register configures all port IB
outputs to have reduced drive levels. Levels are at normal drive