November 10, 1998
GENERAL RELEASE SPECIFICATION
MC68HC05LJ5
INPUT/OUTPUT PORTS
MOTOROLA
REV 1
7-3
7.2.3 Port A Pull-down/up Register
All Port A I/O pins may have software programmable pull-down/up devices
enabled by the applicable mask option. If the pull-down/up mask option is
selected, the pull-down/up is activated whenever the corresponding bit in the
PDURA is clear. If the corresponding bit in the PDURA bit is set or the mask
option for pull-down/up is not chosen, the pull-down/up will be disabled. A pull-
down on an I/O pin is activated only if the I/O pin is programmed as an input
whereas a Pull-up device on an I/O pin is always activated whenever enabled,
regardless of port direction.
The PDURA is a write-only register. Any reads of location $0010 will return unde-
ned results. Since reset clears both the DDRA and the PDURA, all pins will ini-
tialize as inputs with the pull-down active and pull-up devices active (if enabled by
mask option).
Typical value of port A pull-up is 5K
.
7.2.4 Port A Drive Capability
The outputs for the upper four bits of Port A (PA4, PA5, PA6 and PA7) are capable
of sinking approximately 8 mA of current to VSS.
7.2.5 Port A I/O Pin Interrupts
The inputs to PA0, PA1, PA2, PA3 may be connected to the IRQ input of the CPU
if enabled by a mask option. The input to PA7 is also connected to the IRQ input of
the CPU, yet it is only enabled or disabled by software, not by mask option. PA7
interrupt capability is controlled by a set of control and status bits (IRQE1, IRQF1,
IRQR1), different from the set of control and status bits for that of PA0-PA3 and
IRQ pin (IRQE, IRQF, IRQR) in the same ICSR (Interrupt Control and Status Reg-
ister).
When connected as an alternate source of an IRQ interrupt, PA0-3 input pins will
behave the same as the IRQ pin itself, except that their active state is a logical one
or a rising edge. The IRQ pin has an active state that is a logical zero or a falling
edge. PA7 interrupt occurs, if enabled, only upon the falling edge at the input.
If mask options for both level and edge sensitivity interrupts are chosen, the pres-
ence of a logic one or occurrence of a rising edge on any one of the lower four
Port A pins will cause an IRQ interrupt request. If the edge-only sensitivity is
selected, the occurrence of a rising edge on any one of the lower four Port A pins
will cause an IRQ interrupt request. As long as any one of the lower four Port A
IRQ inputs remains at a logic one level, the other of the lower four Port A IRQ
inputs are effectively ignored.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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