MC9S08SH32CWL Datasheet, PDF (63/328 Pages) Freescale Semiconductor, Inc – MC9S08SH32 Series Features

Chapter 5 Resets, Interrupts, and General System Control
The status flag corresponding to the interrupt source must be acknowledged (cleared) before returning
from the ISR. Typically, the flag is cleared at the beginning of the ISR so that if another interrupt is
generated by this same source, it will be registered so it can be serviced after completion of the current ISR.
5.5.2 External Interrupt Request Pin (IRQ)
External interrupts are managed by the IRQ status and control register, IRQSC. When the IRQ function is
enabled, synchronous logic monitors the pin for edge-only or edge-and-level events. When the MCU is in
stop mode and system clocks are shut down, a separate asynchronous path is used so the IRQ (if enabled)
can wake the MCU.
5.5.2.1 Pin Configuration Options
The IRQ pin enable (IRQPE) control bit in IRQSC must be 1 in order for the IRQ pin to act as the interrupt
request (IRQ) input. As an IRQ input, the user can choose the polarity of edges or levels detected
(IRQEDG), whether the pin detects edges-only or edges and levels (IRQMOD), and whether an event
causes an interrupt or only sets the IRQF flag which can be polled by software.
The IRQ pin, when enabled, defaults to use an internal pull device (IRQPDD = 0), the device is a pull-up
or pull-down depending on the polarity chosen. If the user desires to use an external pull-up or pull-down,
the IRQPDD can be written to a 1 to turn off the internal device.
BIH and BIL instructions may be used to detect the level on the IRQ pin when the pin is configured to act
as the IRQ input.
NOTE
This pin does not contain a clamp diode to V_DD and should not be driven
above V_DD.
The voltage measured on the internally pulled up IRQ pin will not be pulled
to V_DD. The internal gates connected to this pin are pulled to V_DD. If the
IRQ pin is required to drive to a V_DD level an external pullup should be used.
5.5.2.2 Edge and Level Sensitivity
The IRQMOD control bit reconfigures the detection logic so it detects edge events and pin levels. In the
edge and level detection mode, the IRQF status flag becomes set when an edge is detected (when the IRQ
pin changes from the deasserted to the asserted level), but the flag is continuously set (and cannot be
cleared) as long as the IRQ pin remains at the asserted level.
5.5.3 Interrupt Vectors, Sources, and Local Masks
Table 5-2 provides a summary of all interrupt sources. Higher-priority sources are located toward the
bottom of the table. The high-order byte of the address for the interrupt service routine is located at the
first address in the vector address column, and the low-order byte of the address for the interrupt service
routine is located at the next higher address.
MC9S08SH32 Series Data Sheet, Rev. 2
Freescale Semiconductor
63
PRELIMINARY