MC912DG128A Motorola, MC912DG128A Datasheet - Page 42

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

Port E
Pinout and Signal Descriptions
MC68HC912DT128A Rev 2.0
42
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 zeroes.
When the PUPB bit in the PUCR register is set, all port B input pins are
pulled-up internally by an active pull-up device. PUCR is not in the
address map in peripheral mode.
Setting the RDPB bit in register RDRIV causes all port B 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 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 (PE[1:0]) can only be
used 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.
The PEAR register determines pin function, and register DDRE
determines whether each pin is an input or output when it is used for
general-purpose I/O. PEAR settings override DDRE settings. Because
PE[1:0] are input-only pins, only DDRE[7:2] have effect. Setting a bit in
the DDRE register makes the corresponding bit in port E an output;
clearing a bit in the DDRE register makes the corresponding bit in port E
an input. The default reset state of DDRE is all zeroes.
When the PUPE bit in the PUCR register is set, PE[7,3,2,1,0] are pulled
up. PE[7,3,2,0] are active pull-up devices. PUPCR is not in the address
map in peripheral mode.
Neither port E nor DDRE is in the map in peripheral mode or in the
internal map in expanded modes with EME set.
Setting the RDPE bit in register RDRIV causes all port E outputs to have
reduced drive level. RDRIV can be written once after reset. RDRIV is not
Pinout and Signal Descriptions
Bus Control and
MOTOROLA
16-pins