MC68HC908JW32_09 Datasheet, PDF (188/232 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

External Interrupt (IRQ)
14.5 PTE3/D– Pin
The PTE3 pin is configured as an interrupt input to trigger the IRQ interrupt when the following conditions
are satisfied:
• The USB module is disabled
• PTE3 pin configured for external interrupt input (PTE3IE = 1)
Setting PTE3IE configures the PTE3 pin to an input pin with an internal pullup device. The PTE3 interrupt
is "ORed" with the IRQ input to trigger the IRQ interrupt Figure 14-1. Therefore, the IRQ status and control
register affects both the IRQ pin and the PTE pin. An interrupt on PTE3 also sets the PTE3 interrupt flag,
PTE3IF, in the IRQ option control register (IOCR).
14.6 IRQ Module During Break Interrupts
The system integration module (SIM) controls whether the IRQ latch can be cleared during the break
state. The BCFE bit in the break flag control register (BFCR) enables software to clear the latches during
the break state. (See Chapter 6 System Integration Module (SIM).)
To allow software to clear the IRQIRQ latch during a break interrupt, write a logic 1 to the BCFE bit. If a
latch is cleared during the break state, it remains cleared when the MCU exits the break state.
To protect the latches during the break state, write a logic 0 to the BCFE bit. With BCFE at logic 0 (its
default state), writing to the ACK bit in the IRQ status and control register during the break state has no
effect on the IRQ latch.
14.7 IRQ Status and Control Register
The IRQ status and control register (ISCR) controls and monitors operation of the IRQ module. The ISCR
has the following functions:
• Shows the state of the IRQ flag
• Clears the IRQ latch
• Masks IRQ interrupt request
• Controls triggering sensitivity of the IRQ pin
Address:
Read:
Write:
Reset:
$001E
Bit 7
6
5
4
3
2
1
0
0
0
0
IRQF
0
IMASK
ACK
0
0
0
0
0
0
0
= Unimplemented
Figure 14-3. IRQ Status and Control Register (ISCR)
Bit 0
MODE
0
IRQF — IRQ Flag
This read-only status bit is high when the IRQ interrupt is pending.
1 = IRQ interrupt pending
0 = IRQ interrupt not pending
MC68HC908JW32 Data Sheet, Rev. 6
188
Freescale Semiconductor