XC912BC32CFU8 Motorola Semiconductor Products, XC912BC32CFU8 Datasheet - Page 34

• Manufacturer Part Number: XC912BC32CFU8
• Description: M68HC12B Family Data Sheet
• Manufacturer: Motorola Semiconductor Products

General Description
1.6.4.1 Port A
1.6.4.2 Port B
1.6.4.3 Port E
Data Sheet
34
Port A pins are used for address and data in expanded modes. 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.
The port A data direction 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 0s.
When the PUPA bit in the PUCR register is set, all port A input pins are pulled up
internally by an active pullup device. This bit has no effect if the port is being used
in expanded modes as the pullups are inactive.
Setting the RDPA bit in the reduced drive register (RDRIV) causes all port A
outputs to have reduced drive levels. RDRIV can be written once after reset and is
not in the address map in peripheral mode. Refer to Section 6. Bus Control and
Input/Output (I/O).
Port B pins are used for address and data in expanded modes. 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.
The port B data direction register (DDRB) determines whether each port B pin is
an input or output. DDRB is not in the address map during expanded and
peripheral mode operation. Setting a bit in DDRB makes the corresponding bit in
port B an output; clearing a bit in DDRB makes the corresponding bit in port B an
input. The default reset state of DDRB is all 0s.
When the PUPB bit in the PUCR register is set, all port B input pins are pulled up
internally by an active pullup device. This bit has no effect if the port is being used
in expanded modes because the pullups are inactive.
Setting the RDPB bit in register RDRIV causes all port B outputs to have reduced
drive levels. RDRIV can be written once after reset. RDRIV is not in the address
map in peripheral mode. Refer to Section 6. Bus Control and Input/Output (I/O).
Port E pins operate differently from port A and B pins. Port E pins are used for bus
control signals and interrupt service request signals. When a pin is not used for one
of these specific functions, it can be used as general-purpose I/O. However, two of
the pins, PE1 and PE0, can be used only for input, and the states of these pins can
be read in the port data register even when they are used for IRQ and XIRQ.
General Description
M68HC12B Family — Rev. 8.0
MOTOROLA