MC912DG128A Motorola, MC912DG128A Datasheet - Page 41

• Manufacturer Part Number: MC912DG128A
• Description: Microcontrollers
• Manufacturer: Motorola

Port Signals
Port A
Port B
15-pins
MOTOROLA
The MC68HC912DT128A incorporates eleven ports which are used to
control and access the various device subsystems. When not used for
these purposes, port pins may be used for general-purpose I/O. In
addition to the pins described below, each port consists of a data register
which can be read and written at any time, and, with the exception of port
AD0, port AD1, PE[1:0], RxCAN and TxCAN, a data direction register
which controls the direction of each pin. After reset all general purpose
I/O pins are configured as input.
Port A pins are used for address and data in expanded modes. When
this port is not used for external access such as in single-chip mode,
these pins can be used as general purpose I/O. The port data register is
not in the address map during expanded and peripheral mode operation.
When it is in the map, port A can be read or written at anytime.
Register DDRA determines whether each port A pin is an input or output.
DDRA is not in the address map during expanded and peripheral mode
operation. Setting a bit in DDRA makes the corresponding bit in port A
an output; clearing a bit in DDRA makes the corresponding bit in port A
an input. The default reset state of DDRA is all zeroes.
When the PUPA bit in the PUCR register is set, all port A input pins are
pulled-up internally by an active pull-up device. PUCR is not in the
address map in peripheral mode.
Setting the RDPA bit in register RDRIV causes all port A 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
Input/Output.
Port B pins are used for address and data in expanded modes. When
this port is not used for external access such as in single-chip mode,
these pins can be used as general purpose I/O. The port data register is
not in the address map during expanded and peripheral mode operation.
When it is in the map, port B can be read or written at anytime.
Pinout and Signal Descriptions
Pinout and Signal Descriptions
MC68HC912DT128A Rev 2.0
Bus Control and
Port Signals
41