Datasheet

Chapter 5 Resets, Interrupts, and General System Control
MC9S08QG8 and MC9S08QG4 Data Sheet, Rev. 5
Freescale Semiconductor 67
5.8.1 Interrupt Pin Request Status and Control Register (IRQSC)
This direct page register includes status and control bits, which are used to configure the IRQ function,
report status, and acknowledge IRQ events.
765
1
1
Bit 5 is a reserved bit that must always be written to 0.
43210
R0
IRQPDD 0IRQPE
IRQF 0
IRQIE IRQMOD
W IRQACK
Reset00000000
= Unimplemented or Reserved
Figure 5-2. Interrupt Request Status and Control Register (IRQSC)
Table 5-3. IRQSC Register Field Descriptions
Field Description
6
IRQPDD
Interrupt Request (IRQ) Pull Device Disable — This read/write control bit is used to disable the internal pullup
device when the IRQ
pin is enabled (IRQPE = 1) allowing for an external device to be used.
0IRQ pull device enabled if IRQPE = 1.
1IRQ pull device disabled if IRQPE = 1.
4
IRQPE
IRQ Pin Enable — This read/write control bit enables the IRQ pin function. When this bit is set the IRQ pin can
be used as an interrupt request.
0IRQ
pin function is disabled.
1IRQ pin function is enabled.
3
IRQF
IRQ Flag — This read-only status bit indicates when an interrupt request event has occurred.
0 No IRQ request.
1 IRQ event detected.
2
IRQACK
IRQ Acknowledge — This write-only bit is used to acknowledge interrupt request events (write 1 to clear IRQF).
Writing 0 has no meaning or effect. Reads always return 0. If edge-and-level detection is selected (IRQMOD = 1),
IRQF cannot be cleared while the IRQ
pin remains at its asserted level.
1
IRQIE
IRQ Interrupt Enable — This read/write control bit determines whether IRQ events generate an interrupt
request.
0 Interrupt request when IRQF set is disabled (use polling).
1 Interrupt requested whenever IRQF = 1.
0
IRQMOD
IRQ Detection Mode — This read/write control bit selects either edge-only detection or edge-and-level
detection. See Section 5.5.2.2, “Edge and Level Sensitivity,” for more details.
0 IRQ event on falling edges only.
1 IRQ event on falling edges and low levels.