mc68hc05j5ap Freescale Semiconductor, Inc, mc68hc05j5ap Datasheet - Page 32

• Manufacturer Part Number: mc68hc05j5ap
• Description: General Description The Mc68hc05j5a Is A Member Of The Low-cost High-performance M68hc05 Family Of 8-bit Microcontroller Units Mcus . The M68hc05 Family Is Based On The Customer-speci Ed Integrated Circuit Design Strategy. All Mcus In The Family
• Manufacturer: Freescale Semiconductor, Inc

GENERAL RELEASE SPECIFICATION
4.5.2 OPTIONAL EXTERNAL INTERRUPTS (PA0-PA3)
4-6
IRQF - IRQ Interrupt Request Flag
Writing to the IRQF flag bit will have no effect on it. If the additional setting of IRQF
flag bit is not cleared in the IRQ service routine and the IRQE enable bit remains
set the CPU will re-enter the IRQ interrupt sequence continuously until either the
IRQF flag bit or the IRQE enable bit is clear. The IRQF latch is cleared by reset.
IRQE1 - PA7 Interrupt Enable
IRQE - IRQ Interrupt Enable
The IRQ interrupt can also be triggered by the inputs on the PA0 thru PA3 port
pins if enabled by a single mask option. If enabled, the lower four bits of Port A
can activate the IRQ interrupt function, and the interrupt operation will be the
same as for inputs to the IRQ pin. This mask option of PA0-3 interrupt allow all of
these input pins to be OR’ed with the input present on the IRQ pin. All PA0 thru
PA3 pins must be selected as a group as an additional IRQ interrupt. All the PA0-3
interrupt sources are also controlled by the IRQE enable bit.
The IRQE1 bit enables/disables the IRQF1 flag bit to initiate an IRQ interrupt
sequence.
The IRQE bit enables/disables the IRQF flag bit to initiate an IRQ interrupt
sequence.
1 = Indicates that an IRQ request is pending.
0 = Indicates that no IRQ request triggered by pins PA0-3 or IRQ is
1 = Enables IRQF1 interrupt, that is, the IRQF1 flag bit can generate an
0 = The IRQF1 flag bit cannot generate an interrupt sequence. Reset
1 = Enables IRQF interrupt, that is, the IRQF flag bit can generate an
0 = The IRQF flag bit cannot generate an interrupt sequence.
pending. The IRQF flag bit is cleared once the IRQ vector is fetched
AND if IRQE1 is also cleared. If IRQE1 is set, then the only way of
clearing IRQF flag is by writing a logic one to IRQR bit. The IRQF
flag bit can be cleared, regardless of the status of the IRQE1 bit, by
writing a logic one to the IRQR acknowledge bit to clear the IRQ
latch and also conditioning the external IRQ sources to be inactive
(if the level sensitive interrupts are enabled via mask option). Doing
so before exiting the service routine will mask out additional
occurrences of the IRQF.
interrupt sequence. Execution of the STOP or WAIT instructions will
leave the IRQE1 bit to be UNAFFECTED.
clears the IRQE1 enable bit, thereby disabling PA7 interrupts.
interrupt sequence. Reset sets the IRQE enable bit, thereby
enabling IRQ interrupts once the I-bit is cleared. Execution of the
STOP or WAIT instructions causes the IRQE bit to be set in order to
allow the external IRQ to exit these modes.
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
July 16, 1999
INTERRUPTS
MC68HC05J5A
REV 2.1