MC68HC901P MOTOROLA [Motorola, Inc], MC68HC901P Datasheet - Page 37

• Manufacturer Part Number: MC68HC901P
• Description: Multi-Function Peripheral
• Manufacturer: MOTOROLA [Motorola, Inc]

General Purpose Input/Output Port
the active edge register will cause the associated input to generate an interrupt on the one-
to-zero transition. Writing a one to the edge bit will produce an interrupt on the zero-to-one
transition of the corresponding line. When the processor sets a bit, interrupts will be
generated on the rising edge of the associated input signal. When the processor clears a bit,
interrupts will be generated on the falling edge of the associated input signal.
GPIP7-GPIP0 – General Purpose I/O Port
5.1.3 Data Direction Register (DDR)
The data direction register (DDR) allows the programmer to define I0 through I7 as inputs
or outputs by writing the corresponding bit. When a bit of the data direction register is written
as a zero, the corresponding interrupt I/O pin will be a high-impedance input. Writing a one
to any bit of the data direction register will cause the corresponding pin to be configured as
a push-pull output.
GPIP7-GPIP0 – General Purpose I/O Port
5-2
AER REGISTER
DDR REGISTER
RESET
RESET
FIELD
FIELD
ADDR
ADDR
BIT
BIT
0 = Interrupts will be generated on the falling edge of the associated input signal.
1 = Interrupts will be generated on the rising edge of the associated input signal.
0 = Associated I/O line is defined to be an input.
1 = Associated I/O line is defined to be an output.
GPIP7
GPIP7
7
0
The inputs to the exclusive-OR of the transition detector are the
edge bit and the input buffer. As a result, writing the AER may
cause an interrupt-producing transition, depending upon the
state of the input. So, the AER should be configured before
enabling interrupts via the interrupt enable registers (IERA and
IERB). Also, changing the edge bit while interrupts are enabled
may cause an interrupt on the corresponding channel.
7
0
GPIP6
GPIP6
6
0
6
0
GPIP5
GPIP5
MC68HC901 USER’S MANUAL
5
5
0
0
GPIP4
NOTE
GPIP4
4
4
0
0
$03
$05
GPIP3
GPIP3
3
0
3
0
GPIP2
GPIP2
2
0
2
0
GPIP1
GPIP1
1
0
1
0
MOTOROLA
GPIP0
GPIP0
0
0
0
0