Advance Information MC68HC908MR16/MC68HC908MR32 — Rev. 4.0
334 External Interrupt (IRQ) MOTOROLA
External Interrupt (IRQ)
17.6 IRQ Status and Control Register
The IRQ status and control register (ISCR) has these functions:
Clears the IRQ interrupt latch
Masks IRQ interrupt requests
Controls triggering sensitivity of the IRQ interrupt pin
ACK1 — IRQ Interrupt Request Acknowledge Bit
Writing a logic 1 to this write-only bit clears the IRQ latch. ACK1
always reads as logic 0. Reset clears ACK1.
IMASK1 — IRQ Interrupt Mask Bit
Writing a logic 1 to this read/write bit d isables IR Q interr upt req uests.
Reset clears IMASK1.
1 = IRQ interrupt requests disabled
0 = IRQ interrupt requests enabled
MODE1 — IRQ Edge/Level Select Bit
This read/write bit controls the triggering sensitivity of the IRQ pin.
Reset clears MODE1.
1 = IRQ interrupt requests on falling edges and low levels
0 = IRQ interrupt requests on falling edges only
IRQF — IRQ Flag
This read-only bit acts as a status flag, indicating an IRQ event
occurred.
1 = External IRQ event occurred.
0 = External IRQ event did not occur.
Address: $003F
Bit 7654321Bit 0
Read: 0000
IRQF 0IMASK1 MODE1
Write:RRRR ACK1
Reset:00000000
R= Reserved
Figure 17-4. IRQ Status and Control Register (ISCR)